diff --git a/docs/source/usage/workflows/ionization.rst b/docs/source/usage/workflows/ionization.rst
index a3540215600..b13f9407320 100644
--- a/docs/source/usage/workflows/ionization.rst
+++ b/docs/source/usage/workflows/ionization.rst
@@ -69,13 +69,13 @@ To include charge-state-only simulations in your simulations you must:
                 float_X,
                 7, // number charge states
                 Nitrogen, // name you may reference this by later, remember to prepend the namespace and append _t!
-                14.53413 * UNITCONV_eV_to_AU,
-                29.60125 * UNITCONV_eV_to_AU,
-                47.4453 * UNITCONV_eV_to_AU,
-                77.4735 * UNITCONV_eV_to_AU,
-                97.89013 * UNITCONV_eV_to_AU,
-                552.06731 * UNITCONV_eV_to_AU,
-                667.04609 * UNITCONV_eV_to_AU);
+                sim.si.conv.ev2auEnergy(14.53413),
+                sim.si.conv.ev2auEnergy(29.60125),
+                sim.si.conv.ev2auEnergy(47.4453),
+                sim.si.conv.ev2auEnergy(77.4735),
+                sim.si.conv.ev2auEnergy(97.89013),
+                sim.si.conv.ev2auEnergy(552.06731),
+                sim.si.conv.ev2auEnergy(667.04609));
         }; // namespace picongpu::ionization::energies::AU
 
     .. note::
diff --git a/include/picongpu/defines.hpp b/include/picongpu/defines.hpp
index d16cfec7b11..8cd449d9f82 100644
--- a/include/picongpu/defines.hpp
+++ b/include/picongpu/defines.hpp
@@ -40,5 +40,4 @@ namespace picongpu
 #include "picongpu/param/speciesConstants.param"
 #include "picongpu/param/simulation.param"
 #include "picongpu/unitless/simulation.unitless"
-#include "picongpu/unitless/physicalConstants.unitless"
 // clang-format on
diff --git a/include/picongpu/param/ionizationEnergies.param b/include/picongpu/param/ionizationEnergies.param
index 15bf40a5de0..bde5391c4da 100644
--- a/include/picongpu/param/ionizationEnergies.param
+++ b/include/picongpu/param/ionizationEnergies.param
@@ -39,7 +39,7 @@ namespace picongpu
          * Please follow these rules for defining ionization energies of atomic species,
          * unless your chosen ionization model requires a different unit system than `AU::`
          *     - input of values in either atomic units or converting eV or Joule to them
-         *     -> use either UNITCONV_eV_to_AU or SI::ATOMIC_UNIT_ENERGY for that purpose
+         *     -> use either sim.si.conv.ev2auEnergy() or sim.si.conv.joule2auEnergy() for that purpose
          *     - use `float_X` as the preferred data type
          *
          * example:
@@ -72,211 +72,216 @@ namespace picongpu
             namespace AU
             {
                 /* ionization energy for ground state hydrogen in atomic units */
-                PMACC_CONST_VECTOR(float_X, 1, Hydrogen, 13.59843 * UNITCONV_eV_to_AU);
+                PMACC_CONST_VECTOR(float_X, 1, Hydrogen, sim.si.conv.ev2auEnergy(13.59843));
 
                 /* ionization energy for ground state deuterium in atomic units */
-                PMACC_CONST_VECTOR(float_X, 1, Deuterium, 13.60213 * UNITCONV_eV_to_AU);
+                PMACC_CONST_VECTOR(float_X, 1, Deuterium, sim.si.conv.ev2auEnergy(13.60213));
 
                 /* ionization energy for ground state helium in atomic units */
-                PMACC_CONST_VECTOR(float_X, 2, Helium, 24.58739 * UNITCONV_eV_to_AU, 54.41776 * UNITCONV_eV_to_AU);
+                PMACC_CONST_VECTOR(
+                    float_X,
+                    2,
+                    Helium,
+                    sim.si.conv.ev2auEnergy(24.58739),
+                    sim.si.conv.ev2auEnergy(54.41776));
 
                 /* ionization energy for carbon in atomic units */
                 PMACC_CONST_VECTOR(
                     float_X,
                     6,
                     Carbon,
-                    11.2603 * UNITCONV_eV_to_AU,
-                    24.3845 * UNITCONV_eV_to_AU,
-                    47.88778 * UNITCONV_eV_to_AU,
-                    64.49351 * UNITCONV_eV_to_AU,
-                    392.0905 * UNITCONV_eV_to_AU,
-                    489.993177 * UNITCONV_eV_to_AU);
+                    sim.si.conv.ev2auEnergy(11.2603),
+                    sim.si.conv.ev2auEnergy(24.3845),
+                    sim.si.conv.ev2auEnergy(47.88778),
+                    sim.si.conv.ev2auEnergy(64.49351),
+                    sim.si.conv.ev2auEnergy(392.0905),
+                    sim.si.conv.ev2auEnergy(489.993177));
 
                 /* ionization energy for nitrogen in atomic units */
                 PMACC_CONST_VECTOR(
                     float_X,
                     7,
                     Nitrogen,
-                    14.53413 * UNITCONV_eV_to_AU,
-                    29.60125 * UNITCONV_eV_to_AU,
-                    47.4453 * UNITCONV_eV_to_AU,
-                    77.4735 * UNITCONV_eV_to_AU,
-                    97.89013 * UNITCONV_eV_to_AU,
-                    552.06731 * UNITCONV_eV_to_AU,
-                    667.04609 * UNITCONV_eV_to_AU);
+                    sim.si.conv.ev2auEnergy(14.53413),
+                    sim.si.conv.ev2auEnergy(29.60125),
+                    sim.si.conv.ev2auEnergy(47.4453),
+                    sim.si.conv.ev2auEnergy(77.4735),
+                    sim.si.conv.ev2auEnergy(97.89013),
+                    sim.si.conv.ev2auEnergy(552.06731),
+                    sim.si.conv.ev2auEnergy(667.04609));
 
                 /* ionization energy for oxygen in atomic units */
                 PMACC_CONST_VECTOR(
                     float_X,
                     8,
                     Oxygen,
-                    13.61805 * UNITCONV_eV_to_AU,
-                    35.12112 * UNITCONV_eV_to_AU,
-                    54.93554 * UNITCONV_eV_to_AU,
-                    77.41350 * UNITCONV_eV_to_AU,
-                    113.8989 * UNITCONV_eV_to_AU,
-                    138.1189 * UNITCONV_eV_to_AU,
-                    739.3268 * UNITCONV_eV_to_AU,
-                    871.4098 * UNITCONV_eV_to_AU);
+                    sim.si.conv.ev2auEnergy(13.61805),
+                    sim.si.conv.ev2auEnergy(35.12112),
+                    sim.si.conv.ev2auEnergy(54.93554),
+                    sim.si.conv.ev2auEnergy(77.41350),
+                    sim.si.conv.ev2auEnergy(113.8989),
+                    sim.si.conv.ev2auEnergy(138.1189),
+                    sim.si.conv.ev2auEnergy(739.3268),
+                    sim.si.conv.ev2auEnergy(871.4098));
 
                 /* ionization energy for aluminium in atomic units */
                 PMACC_CONST_VECTOR(
                     float_X,
                     13,
                     Aluminium,
-                    5.98577 * UNITCONV_eV_to_AU,
-                    18.8285 * UNITCONV_eV_to_AU,
-                    28.4476 * UNITCONV_eV_to_AU,
-                    119.992 * UNITCONV_eV_to_AU,
-                    153.825 * UNITCONV_eV_to_AU,
-                    190.495 * UNITCONV_eV_to_AU,
-                    241.769 * UNITCONV_eV_to_AU,
-                    284.647 * UNITCONV_eV_to_AU,
-                    330.214 * UNITCONV_eV_to_AU,
-                    398.656 * UNITCONV_eV_to_AU,
-                    442.006 * UNITCONV_eV_to_AU,
-                    2085.97 * UNITCONV_eV_to_AU,
-                    2304.14 * UNITCONV_eV_to_AU);
+                    sim.si.conv.ev2auEnergy(5.98577),
+                    sim.si.conv.ev2auEnergy(18.8285),
+                    sim.si.conv.ev2auEnergy(28.4476),
+                    sim.si.conv.ev2auEnergy(119.992),
+                    sim.si.conv.ev2auEnergy(153.825),
+                    sim.si.conv.ev2auEnergy(190.495),
+                    sim.si.conv.ev2auEnergy(241.769),
+                    sim.si.conv.ev2auEnergy(284.647),
+                    sim.si.conv.ev2auEnergy(330.214),
+                    sim.si.conv.ev2auEnergy(398.656),
+                    sim.si.conv.ev2auEnergy(442.006),
+                    sim.si.conv.ev2auEnergy(2085.97),
+                    sim.si.conv.ev2auEnergy(2304.14));
 
                 /* ionization energy for silicon in atomic units */
                 PMACC_CONST_VECTOR(
                     float_X,
                     14,
                     Silicon,
-                    8.151683 * UNITCONV_eV_to_AU,
-                    16.345845 * UNITCONV_eV_to_AU,
-                    33.493 * UNITCONV_eV_to_AU,
-                    45.14179 * UNITCONV_eV_to_AU,
-                    166.767 * UNITCONV_eV_to_AU,
-                    205.267 * UNITCONV_eV_to_AU,
-                    246.32 * UNITCONV_eV_to_AU,
-                    303.66 * UNITCONV_eV_to_AU,
-                    351.1 * UNITCONV_eV_to_AU,
-                    401.38 * UNITCONV_eV_to_AU,
-                    476.18 * UNITCONV_eV_to_AU,
-                    523.415 * UNITCONV_eV_to_AU,
-                    2437.65804 * UNITCONV_eV_to_AU,
-                    2673.1774 * UNITCONV_eV_to_AU);
+                    sim.si.conv.ev2auEnergy(8.151683),
+                    sim.si.conv.ev2auEnergy(16.345845),
+                    sim.si.conv.ev2auEnergy(33.493),
+                    sim.si.conv.ev2auEnergy(45.14179),
+                    sim.si.conv.ev2auEnergy(166.767),
+                    sim.si.conv.ev2auEnergy(205.267),
+                    sim.si.conv.ev2auEnergy(246.32),
+                    sim.si.conv.ev2auEnergy(303.66),
+                    sim.si.conv.ev2auEnergy(351.1),
+                    sim.si.conv.ev2auEnergy(401.38),
+                    sim.si.conv.ev2auEnergy(476.18),
+                    sim.si.conv.ev2auEnergy(523.415),
+                    sim.si.conv.ev2auEnergy(2437.65804),
+                    sim.si.conv.ev2auEnergy(2673.1774));
 
                 /* ionization energy for copper in atomic units */
                 PMACC_CONST_VECTOR(
                     float_X,
                     29,
                     Copper,
-                    7.72638 * UNITCONV_eV_to_AU,
-                    20.2924 * UNITCONV_eV_to_AU,
-                    36.8411 * UNITCONV_eV_to_AU,
-                    57.385 * UNITCONV_eV_to_AU,
-                    79.87 * UNITCONV_eV_to_AU,
-                    103.010 * UNITCONV_eV_to_AU,
-                    139.012 * UNITCONV_eV_to_AU,
-                    166.021 * UNITCONV_eV_to_AU,
-                    198.022 * UNITCONV_eV_to_AU,
-                    232.25 * UNITCONV_eV_to_AU,
-                    265.332 * UNITCONV_eV_to_AU,
-                    367.09 * UNITCONV_eV_to_AU,
-                    401.03 * UNITCONV_eV_to_AU,
-                    436.06 * UNITCONV_eV_to_AU,
-                    483.19 * UNITCONV_eV_to_AU,
-                    518.712 * UNITCONV_eV_to_AU,
-                    552.821 * UNITCONV_eV_to_AU,
-                    632.56 * UNITCONV_eV_to_AU,
-                    670.608 * UNITCONV_eV_to_AU,
-                    1690.59 * UNITCONV_eV_to_AU,
-                    1800.3 * UNITCONV_eV_to_AU,
-                    1918.4 * UNITCONV_eV_to_AU,
-                    2044.6 * UNITCONV_eV_to_AU,
-                    2179.4 * UNITCONV_eV_to_AU,
-                    2307.32 * UNITCONV_eV_to_AU,
-                    2479.12 * UNITCONV_eV_to_AU,
-                    2586.95 * UNITCONV_eV_to_AU,
-                    11062.4 * UNITCONV_eV_to_AU,
-                    11567.6 * UNITCONV_eV_to_AU);
+                    sim.si.conv.ev2auEnergy(7.72638),
+                    sim.si.conv.ev2auEnergy(20.2924),
+                    sim.si.conv.ev2auEnergy(36.8411),
+                    sim.si.conv.ev2auEnergy(57.385),
+                    sim.si.conv.ev2auEnergy(79.87),
+                    sim.si.conv.ev2auEnergy(103.010),
+                    sim.si.conv.ev2auEnergy(139.012),
+                    sim.si.conv.ev2auEnergy(166.021),
+                    sim.si.conv.ev2auEnergy(198.022),
+                    sim.si.conv.ev2auEnergy(232.25),
+                    sim.si.conv.ev2auEnergy(265.332),
+                    sim.si.conv.ev2auEnergy(367.09),
+                    sim.si.conv.ev2auEnergy(401.03),
+                    sim.si.conv.ev2auEnergy(436.06),
+                    sim.si.conv.ev2auEnergy(483.19),
+                    sim.si.conv.ev2auEnergy(518.712),
+                    sim.si.conv.ev2auEnergy(552.821),
+                    sim.si.conv.ev2auEnergy(632.56),
+                    sim.si.conv.ev2auEnergy(670.608),
+                    sim.si.conv.ev2auEnergy(1690.59),
+                    sim.si.conv.ev2auEnergy(1800.3),
+                    sim.si.conv.ev2auEnergy(1918.4),
+                    sim.si.conv.ev2auEnergy(2044.6),
+                    sim.si.conv.ev2auEnergy(2179.4),
+                    sim.si.conv.ev2auEnergy(2307.32),
+                    sim.si.conv.ev2auEnergy(2479.12),
+                    sim.si.conv.ev2auEnergy(2586.95),
+                    sim.si.conv.ev2auEnergy(11062.4),
+                    sim.si.conv.ev2auEnergy(11567.6));
 
                 /* ionization energy for gold in atomic units */
                 PMACC_CONST_VECTOR(
                     float_X,
                     79,
                     Gold,
-                    9.2256 * UNITCONV_eV_to_AU,
-                    20.203 * UNITCONV_eV_to_AU,
-                    30.016 * UNITCONV_eV_to_AU,
-                    45.017 * UNITCONV_eV_to_AU,
-                    60.019 * UNITCONV_eV_to_AU,
-                    74.020 * UNITCONV_eV_to_AU,
-                    94.020 * UNITCONV_eV_to_AU,
-                    112.02 * UNITCONV_eV_to_AU,
-                    130.12 * UNITCONV_eV_to_AU,
-                    149.02 * UNITCONV_eV_to_AU,
-                    168.21 * UNITCONV_eV_to_AU,
-                    248.01 * UNITCONV_eV_to_AU,
-                    275.14 * UNITCONV_eV_to_AU,
-                    299.15 * UNITCONV_eV_to_AU,
-                    324.16 * UNITCONV_eV_to_AU,
-                    365.19 * UNITCONV_eV_to_AU,
-                    392.20 * UNITCONV_eV_to_AU,
-                    433.21 * UNITCONV_eV_to_AU,
-                    487.25 * UNITCONV_eV_to_AU,
-                    517.30 * UNITCONV_eV_to_AU,
-                    546.30 * UNITCONV_eV_to_AU,
-                    600.30 * UNITCONV_eV_to_AU,
-                    650.40 * UNITCONV_eV_to_AU,
-                    710.40 * UNITCONV_eV_to_AU,
-                    760.40 * UNITCONV_eV_to_AU,
-                    820.40 * UNITCONV_eV_to_AU,
-                    870.40 * UNITCONV_eV_to_AU,
-                    930.50 * UNITCONV_eV_to_AU,
-                    990.50 * UNITCONV_eV_to_AU,
-                    1040.5 * UNITCONV_eV_to_AU,
-                    1100.5 * UNITCONV_eV_to_AU,
-                    1150.6 * UNITCONV_eV_to_AU,
-                    1210.6 * UNITCONV_eV_to_AU,
-                    1475.5 * UNITCONV_eV_to_AU,
-                    1527.5 * UNITCONV_eV_to_AU,
-                    1584.5 * UNITCONV_eV_to_AU,
-                    1644.5 * UNITCONV_eV_to_AU,
-                    1702.4 * UNITCONV_eV_to_AU,
-                    1758.4 * UNITCONV_eV_to_AU,
-                    1845.4 * UNITCONV_eV_to_AU,
-                    1904.4 * UNITCONV_eV_to_AU,
-                    1967.4 * UNITCONV_eV_to_AU,
-                    2026.4 * UNITCONV_eV_to_AU,
-                    2261.4 * UNITCONV_eV_to_AU,
-                    2320.4 * UNITCONV_eV_to_AU,
-                    2383.4 * UNITCONV_eV_to_AU,
-                    2443.4 * UNITCONV_eV_to_AU,
-                    2640.4 * UNITCONV_eV_to_AU,
-                    2708.4 * UNITCONV_eV_to_AU,
-                    2870.4 * UNITCONV_eV_to_AU,
-                    2941.0 * UNITCONV_eV_to_AU,
-                    4888.4 * UNITCONV_eV_to_AU,
-                    5013.4 * UNITCONV_eV_to_AU,
-                    5156.5 * UNITCONV_eV_to_AU,
-                    5307.5 * UNITCONV_eV_to_AU,
-                    5452.5 * UNITCONV_eV_to_AU,
-                    5594.5 * UNITCONV_eV_to_AU,
-                    5846.6 * UNITCONV_eV_to_AU,
-                    5994.6 * UNITCONV_eV_to_AU,
-                    6156.7 * UNITCONV_eV_to_AU,
-                    6305.1 * UNITCONV_eV_to_AU,
-                    6724.1 * UNITCONV_eV_to_AU,
-                    6854.1 * UNITCONV_eV_to_AU,
-                    6997.2 * UNITCONV_eV_to_AU,
-                    7130.2 * UNITCONV_eV_to_AU,
-                    7756.3 * UNITCONV_eV_to_AU,
-                    7910.4 * UNITCONV_eV_to_AU,
-                    8210.4 * UNITCONV_eV_to_AU,
-                    8360.5 * UNITCONV_eV_to_AU,
-                    18040. * UNITCONV_eV_to_AU,
-                    18401. * UNITCONV_eV_to_AU,
-                    18791. * UNITCONV_eV_to_AU,
-                    19151. * UNITCONV_eV_to_AU,
-                    21471. * UNITCONV_eV_to_AU,
-                    21921. * UNITCONV_eV_to_AU,
-                    22500. * UNITCONV_eV_to_AU,
-                    22868. * UNITCONV_eV_to_AU,
-                    91516. * UNITCONV_eV_to_AU,
-                    93254. * UNITCONV_eV_to_AU);
+                    sim.si.conv.ev2auEnergy(9.2256),
+                    sim.si.conv.ev2auEnergy(20.203),
+                    sim.si.conv.ev2auEnergy(30.016),
+                    sim.si.conv.ev2auEnergy(45.017),
+                    sim.si.conv.ev2auEnergy(60.019),
+                    sim.si.conv.ev2auEnergy(74.020),
+                    sim.si.conv.ev2auEnergy(94.020),
+                    sim.si.conv.ev2auEnergy(112.02),
+                    sim.si.conv.ev2auEnergy(130.12),
+                    sim.si.conv.ev2auEnergy(149.02),
+                    sim.si.conv.ev2auEnergy(168.21),
+                    sim.si.conv.ev2auEnergy(248.01),
+                    sim.si.conv.ev2auEnergy(275.14),
+                    sim.si.conv.ev2auEnergy(299.15),
+                    sim.si.conv.ev2auEnergy(324.16),
+                    sim.si.conv.ev2auEnergy(365.19),
+                    sim.si.conv.ev2auEnergy(392.20),
+                    sim.si.conv.ev2auEnergy(433.21),
+                    sim.si.conv.ev2auEnergy(487.25),
+                    sim.si.conv.ev2auEnergy(517.30),
+                    sim.si.conv.ev2auEnergy(546.30),
+                    sim.si.conv.ev2auEnergy(600.30),
+                    sim.si.conv.ev2auEnergy(650.40),
+                    sim.si.conv.ev2auEnergy(710.40),
+                    sim.si.conv.ev2auEnergy(760.40),
+                    sim.si.conv.ev2auEnergy(820.40),
+                    sim.si.conv.ev2auEnergy(870.40),
+                    sim.si.conv.ev2auEnergy(930.50),
+                    sim.si.conv.ev2auEnergy(990.50),
+                    sim.si.conv.ev2auEnergy(1040.5),
+                    sim.si.conv.ev2auEnergy(1100.5),
+                    sim.si.conv.ev2auEnergy(1150.6),
+                    sim.si.conv.ev2auEnergy(1210.6),
+                    sim.si.conv.ev2auEnergy(1475.5),
+                    sim.si.conv.ev2auEnergy(1527.5),
+                    sim.si.conv.ev2auEnergy(1584.5),
+                    sim.si.conv.ev2auEnergy(1644.5),
+                    sim.si.conv.ev2auEnergy(1702.4),
+                    sim.si.conv.ev2auEnergy(1758.4),
+                    sim.si.conv.ev2auEnergy(1845.4),
+                    sim.si.conv.ev2auEnergy(1904.4),
+                    sim.si.conv.ev2auEnergy(1967.4),
+                    sim.si.conv.ev2auEnergy(2026.4),
+                    sim.si.conv.ev2auEnergy(2261.4),
+                    sim.si.conv.ev2auEnergy(2320.4),
+                    sim.si.conv.ev2auEnergy(2383.4),
+                    sim.si.conv.ev2auEnergy(2443.4),
+                    sim.si.conv.ev2auEnergy(2640.4),
+                    sim.si.conv.ev2auEnergy(2708.4),
+                    sim.si.conv.ev2auEnergy(2870.4),
+                    sim.si.conv.ev2auEnergy(2941.0),
+                    sim.si.conv.ev2auEnergy(4888.4),
+                    sim.si.conv.ev2auEnergy(5013.4),
+                    sim.si.conv.ev2auEnergy(5156.5),
+                    sim.si.conv.ev2auEnergy(5307.5),
+                    sim.si.conv.ev2auEnergy(5452.5),
+                    sim.si.conv.ev2auEnergy(5594.5),
+                    sim.si.conv.ev2auEnergy(5846.6),
+                    sim.si.conv.ev2auEnergy(5994.6),
+                    sim.si.conv.ev2auEnergy(6156.7),
+                    sim.si.conv.ev2auEnergy(6305.1),
+                    sim.si.conv.ev2auEnergy(6724.1),
+                    sim.si.conv.ev2auEnergy(6854.1),
+                    sim.si.conv.ev2auEnergy(6997.2),
+                    sim.si.conv.ev2auEnergy(7130.2),
+                    sim.si.conv.ev2auEnergy(7756.3),
+                    sim.si.conv.ev2auEnergy(7910.4),
+                    sim.si.conv.ev2auEnergy(8210.4),
+                    sim.si.conv.ev2auEnergy(8360.5),
+                    sim.si.conv.ev2auEnergy(18040.),
+                    sim.si.conv.ev2auEnergy(18401.),
+                    sim.si.conv.ev2auEnergy(18791.),
+                    sim.si.conv.ev2auEnergy(19151.),
+                    sim.si.conv.ev2auEnergy(21471.),
+                    sim.si.conv.ev2auEnergy(21921.),
+                    sim.si.conv.ev2auEnergy(22500.),
+                    sim.si.conv.ev2auEnergy(22868.),
+                    sim.si.conv.ev2auEnergy(91516.),
+                    sim.si.conv.ev2auEnergy(93254.));
 
             } // namespace AU
         } // namespace energies
diff --git a/include/picongpu/param/physicalConstants.param b/include/picongpu/param/physicalConstants.param
index 2224caa3697..60508097b7a 100644
--- a/include/picongpu/param/physicalConstants.param
+++ b/include/picongpu/param/physicalConstants.param
@@ -46,26 +46,5 @@ namespace picongpu
         constexpr float_64 ELECTRON_MASS_SI = 9.1093837139e-31;
         //! unit: C,    2022 CODATA value, https://physics.nist.gov/cgi-bin/cuu/Value?e
         constexpr float_64 ELECTRON_CHARGE_SI = -1.602176634e-19;
-
-        /* atomic unit for energy:
-         * 2 Rydberg = 27.21 eV --> converted to Joule
-         */
-        constexpr float_64 ATOMIC_UNIT_ENERGY = 4.36e-18;
-
-        /* atomic unit for electric field in V/m:
-         * field strength between electron and core in ground state hydrogen
-         */
-        constexpr float_64 ATOMIC_UNIT_EFIELD = 5.14e11;
-
-        /* atomic unit for time in s:
-         * 150 attoseconds (classical electron orbit time in hydrogen) / 2 PI
-         */
-        constexpr float_64 ATOMIC_UNIT_TIME = 2.4189e-17;
-
     } // namespace SI
-
-    /* 1 atomic unit of energy is equal to 1 Hartree or 2 Rydberg
-     * which is twice the ground state binding energy of atomic hydrogen */
-    constexpr float_64 UNITCONV_AU_to_eV = 27.21139;
-    constexpr float_64 UNITCONV_eV_to_AU = (1.0 / UNITCONV_AU_to_eV);
 } // namespace picongpu
diff --git a/include/picongpu/particles/atomicPhysics/kernel/DecelerateElectrons.kernel b/include/picongpu/particles/atomicPhysics/kernel/DecelerateElectrons.kernel
index dea2dd1a3cf..6083a38d0c6 100644
--- a/include/picongpu/particles/atomicPhysics/kernel/DecelerateElectrons.kernel
+++ b/include/picongpu/particles/atomicPhysics/kernel/DecelerateElectrons.kernel
@@ -142,7 +142,7 @@ namespace picongpu::particles::atomicPhysics::kernel
                     // sqrt(E' * (E' + 2* m*c^2)) / c
                     float_X const newElectronMomentum
                         = math::sqrt(newEnergyElectron * (newEnergyElectron + 2 * mcSquaredElectron)) * scalingFactor;
-                    // AU = ATOMIC_UNIT_ENERGY
+                    // AU = sim.si.conv.auEnergy2Joule()
                     // sqrt(eV * (eV + eV))/(sim.unit.length()/sim.unit.time()) * (sim.unit.energy()/eV)
                     //  = sqrt((eV)^2)/(eV) * sim.unit.time()/sim.unit.length() * sim.unit.energy()
                     //  = sim.unit.mass() * sim.unit.length()^2/sim.unit.time()^2 * sim.unit.time()/sim.unit.length()
diff --git a/include/picongpu/particles/atomicPhysics/rateCalculation/BoundFreeFieldTransitionRates.hpp b/include/picongpu/particles/atomicPhysics/rateCalculation/BoundFreeFieldTransitionRates.hpp
index d291e8fa3f7..8310f6cee13 100644
--- a/include/picongpu/particles/atomicPhysics/rateCalculation/BoundFreeFieldTransitionRates.hpp
+++ b/include/picongpu/particles/atomicPhysics/rateCalculation/BoundFreeFieldTransitionRates.hpp
@@ -92,8 +92,8 @@ namespace picongpu::particles::atomicPhysics::rateCalculation
                 chargeStateDataBox);
             // unitless
             float_X const effectivePrincipalQuantumNumber
-                = screenedCharge / math::sqrt(2._X * ionizationEnergy * picongpu::UNITCONV_eV_to_AU);
-            float_X const eFieldNorm_AU = eFieldNorm / ATOMIC_UNIT_EFIELD;
+                = screenedCharge / math::sqrt(2._X * ionizationEnergy * sim.si.conv.ev2auEnergy(1.0));
+            float_X const eFieldNorm_AU = sim.pic.conv.eField2auEField(eFieldNorm);
             float_X const screenedChargeCubed = pmacc::math::cPow(screenedCharge, 3u);
             float_X const dBase = 4.0_X * math::exp(1._X) * screenedChargeCubed
                 / (eFieldNorm_AU * pmacc::math::cPow(effectivePrincipalQuantumNumber, 4u));
@@ -103,7 +103,7 @@ namespace picongpu::particles::atomicPhysics::rateCalculation
             constexpr float_X pi = pmacc::math::Pi<float_X>::value;
             float_X const nEffCubed = pmacc::math::cPow(effectivePrincipalQuantumNumber, 3u);
 
-            // 1/ATOMIC_UNIT_TIME
+            // 1/atomicTime
             float_X rateADK_AU = eFieldNorm_AU * pmacc::math::cPow(dFromADK, 2u) / (8._X * pi * screenedCharge)
                 * math::exp(-2._X * screenedChargeCubed / (3._X * nEffCubed * eFieldNorm_AU));
 
@@ -112,7 +112,7 @@ namespace picongpu::particles::atomicPhysics::rateCalculation
                 u32(T_ADKLaserPolarization) == u32(atomicPhysics::enums::ADKLaserPolarization::linearPolarization))
                 rateADK_AU *= math::sqrt(3._X * nEffCubed * eFieldNorm_AU / (pi * screenedChargeCubed));
 
-            return rateADK_AU / ATOMIC_UNIT_TIME;
+            return rateADK_AU / sim.pic.conv.auTime2Time(1.0);
         }
     };
 } // namespace picongpu::particles::atomicPhysics::rateCalculation
diff --git a/include/picongpu/particles/ionization/byField/ADK/AlgorithmADK.hpp b/include/picongpu/particles/ionization/byField/ADK/AlgorithmADK.hpp
index a0f1ca36c7f..d5a414847d2 100644
--- a/include/picongpu/particles/ionization/byField/ADK/AlgorithmADK.hpp
+++ b/include/picongpu/particles/ionization/byField/ADK/AlgorithmADK.hpp
@@ -84,7 +84,7 @@ namespace picongpu
 
                         constexpr float_X pi = pmacc::math::Pi<float_X>::value;
                         /* electric field in atomic units - only absolute value */
-                        float_X const eInAU = pmacc::math::l2norm(eField) / ATOMIC_UNIT_EFIELD;
+                        float_X const eInAU = sim.pic.conv.eField2auEField(pmacc::math::l2norm(eField));
 
                         /* the charge that attracts the electron that is to be ionized:
                          * equals `protonNumber - #allInnerElectrons`
@@ -113,7 +113,7 @@ namespace picongpu
                         }
 
                         /* simulation time step in atomic units */
-                        auto const timeStepAU = float_X(sim.pic.getDt() / ATOMIC_UNIT_TIME);
+                        auto const timeStepAU = sim.pic.conv.time2auTime(sim.pic.getDt());
                         /* ionization probability
                          *
                          * probability = rate * time step
diff --git a/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSI.hpp b/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSI.hpp
index 750121da03b..9054a5d7635 100644
--- a/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSI.hpp
+++ b/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSI.hpp
@@ -77,7 +77,7 @@ namespace picongpu
                         /* critical field strength in atomic units */
                         float_X const critField = iEnergy * iEnergy / (float_X(4.0) * effectiveCharge);
                         /* ionization condition */
-                        if(pmacc::math::l2norm(eField) / ATOMIC_UNIT_EFIELD >= critField)
+                        if(sim.pic.conv.eField2auEField(pmacc::math::l2norm(eField)) >= critField)
                         {
                             /* return ionization energy and number of macro electrons to produce */
                             return IonizerReturn{iEnergy, 1u};
diff --git a/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSIEffectiveZ.hpp b/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSIEffectiveZ.hpp
index eb5c330fa22..1a9ffadb89c 100644
--- a/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSIEffectiveZ.hpp
+++ b/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSIEffectiveZ.hpp
@@ -76,7 +76,7 @@ namespace picongpu
                         float_X critField = iEnergy * iEnergy / (float_X(4.0) * ZEff);
 
                         /* ionization condition */
-                        if(pmacc::math::l2norm(eField) / ATOMIC_UNIT_EFIELD >= critField)
+                        if(sim.pic.conv.eField2auEField(pmacc::math::l2norm(eField)) >= critField)
                         {
                             /* return ionization energy and number of macro electrons to produce */
                             return IonizerReturn{iEnergy, 1u};
diff --git a/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSIStarkShifted.hpp b/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSIStarkShifted.hpp
index 46602ed5cad..51684037d3d 100644
--- a/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSIStarkShifted.hpp
+++ b/include/picongpu/particles/ionization/byField/BSI/AlgorithmBSIStarkShifted.hpp
@@ -75,7 +75,7 @@ namespace picongpu
                             = (math::sqrt(float_X(2.)) - float_X(1.)) * math::pow(iEnergy, float_X(3. / 2.));
 
                         /* ionization condition */
-                        if(pmacc::math::l2norm(eField) / ATOMIC_UNIT_EFIELD >= critField)
+                        if(sim.pic.conv.eField2auEField(pmacc::math::l2norm(eField)) >= critField)
                         {
                             /* return ionization energy number of electrons to produce */
                             return IonizerReturn{iEnergy, 1u};
diff --git a/include/picongpu/particles/ionization/byField/IonizationCurrent/IonizationCurrent.hpp b/include/picongpu/particles/ionization/byField/IonizationCurrent/IonizationCurrent.hpp
index c90b7e37909..0c9c790fd6f 100644
--- a/include/picongpu/particles/ionization/byField/IonizationCurrent/IonizationCurrent.hpp
+++ b/include/picongpu/particles/ionization/byField/IonizationCurrent/IonizationCurrent.hpp
@@ -61,8 +61,7 @@ namespace picongpu
                      * ionization current. */
                     if(retValue.ionizationEnergy != 0.0_X)
                     {
-                        auto ionizationEnergy = weighting * retValue.ionizationEnergy * SI::ATOMIC_UNIT_ENERGY
-                            / sim.unit.energy(); // convert to PIConGPU units
+                        auto ionizationEnergy = sim.pic.conv.auEnergy2Joule(weighting * retValue.ionizationEnergy);
                         /* calculate ionization current at particle position */
                         float3_X jIonizationPar = JIonizationCalc{}(ionizationEnergy, eField);
                         /* assign ionization current to grid points */
diff --git a/include/picongpu/particles/ionization/byField/Keldysh/AlgorithmKeldysh.hpp b/include/picongpu/particles/ionization/byField/Keldysh/AlgorithmKeldysh.hpp
index ef626001e33..ac3c7f476aa 100644
--- a/include/picongpu/particles/ionization/byField/Keldysh/AlgorithmKeldysh.hpp
+++ b/include/picongpu/particles/ionization/byField/Keldysh/AlgorithmKeldysh.hpp
@@ -76,7 +76,7 @@ namespace picongpu
 
                         constexpr float_X pi = pmacc::math::Pi<float_X>::value;
                         /* electric field in atomic units - only absolute value */
-                        float_X eInAU = pmacc::math::l2norm(eField) / ATOMIC_UNIT_EFIELD;
+                        float_X eInAU = sim.pic.conv.eField2auEField(pmacc::math::l2norm(eField));
 
                         /* factor two avoid calculation math::pow(2,5./4.); */
                         const float_X twoToFiveQuarters = 2.3784142300054;
@@ -89,7 +89,7 @@ namespace picongpu
                             * math::sqrt(float_X(1.) / charExpArg) * math::exp(-float_X(2. / 3.) * charExpArg);
 
                         /* simulation time step in atomic units */
-                        const auto timeStepAU = float_X(sim.pic.getDt() / ATOMIC_UNIT_TIME);
+                        const auto timeStepAU = sim.pic.conv.time2auTime(sim.pic.getDt());
                         /* ionization probability
                          *
                          * probability = rate * time step
diff --git a/include/picongpu/unitless/simulation.unitless b/include/picongpu/unitless/simulation.unitless
index 6314f31e6f6..ceac3597ab3 100644
--- a/include/picongpu/unitless/simulation.unitless
+++ b/include/picongpu/unitless/simulation.unitless
@@ -127,6 +127,35 @@ namespace picongpu
             {
                 return static_cast<T_Type>(si.getClassicalElectronRadius() / unit.length());
             }
+
+            struct Convert
+            {
+                template<typename T_Type = float_X>
+                constexpr T_Type eField2auEField(T_Type eField = 1.0) const
+                {
+                    return static_cast<T_Type>(si.conv.eField2auEField(eField * unit.eField()));
+                }
+
+                template<typename T_Type = float_X>
+                constexpr T_Type auEnergy2Joule(T_Type auEnergy = 1.0) const
+                {
+                    return static_cast<T_Type>(si.conv.auEnergy2Joule(auEnergy) / unit.energy());
+                }
+
+                template<typename T_Type = float_X>
+                constexpr T_Type auTime2Time(T_Type auTime = 1.0) const
+                {
+                    return static_cast<T_Type>(si.conv.auTime2Time(auTime) / unit.time());
+                }
+
+                template<typename T_Type = float_X>
+                constexpr T_Type time2auTime(T_Type time = 1.0) const
+                {
+                    return static_cast<T_Type>(si.conv.time2auTime(time * unit.time()));
+                }
+            };
+
+            static constexpr Convert conv{};
         };
         struct SiUnits
         {
@@ -289,6 +318,55 @@ namespace picongpu
                 {
                     return joule / ev2Joule(1.0);
                 }
+
+                /* atomic unit for energy:
+                 * 2 Rydberg = 27.21 eV --> converted to Joule
+                 */
+                constexpr float_64 auEnergy2Joule(float_64 auEnergy = 1.0) const
+                {
+                    return auEnergy * 2.0 * si.getRydbergEnergy();
+                }
+
+                constexpr float_64 joule2auEnergy(float_64 joule = 1.0) const
+                {
+                    return joule / auEnergy2Joule(1.0);
+                }
+
+                constexpr float_64 auEnergy2ev(float_64 auEnergy = 1.0) const
+                {
+                    return joule2ev(auEnergy2Joule(auEnergy));
+                }
+
+                constexpr float_64 ev2auEnergy(float_64 ev = 1.0) const
+                {
+                    return ev / auEnergy2ev(1.0);
+                }
+
+                /* atomic unit for electric field in V/m:
+                 * field strength between electron and core in ground state hydrogen
+                 */
+                constexpr float_64 auEField2EField(float_64 auEField = 1.0) const
+                {
+                    return auEField * 5.14e11;
+                }
+
+                constexpr float_64 eField2auEField(float_64 eField = 1.0) const
+                {
+                    return eField / auEField2EField();
+                }
+
+                /* atomic unit for time in s:
+                 * 150 attoseconds (classical electron orbit time in hydrogen) / 2 PI
+                 */
+                constexpr float_64 auTime2Time(float_64 auTime = 1.0) const
+                {
+                    return auTime * 2.4189e-17;
+                }
+
+                constexpr float_64 time2auTime(float_64 time = 1.0) const
+                {
+                    return time / auTime2Time(1.0);
+                }
             };
 
             static constexpr Convert conv{};
diff --git a/share/picongpu/tests/compileAtomicPhysics/include/picongpu/param/ionizationEnergies.param b/share/picongpu/tests/compileAtomicPhysics/include/picongpu/param/ionizationEnergies.param
index f1bd9beccae..bacf5b50f9c 100644
--- a/share/picongpu/tests/compileAtomicPhysics/include/picongpu/param/ionizationEnergies.param
+++ b/share/picongpu/tests/compileAtomicPhysics/include/picongpu/param/ionizationEnergies.param
@@ -39,7 +39,7 @@ namespace picongpu
          * Please follow these rules for defining ionization energies of atomic species,
          * unless your chosen ionization model requires a different unit system than `AU::`
          *     - input of values in either atomic units or converting eV or Joule to them
-         *     -> use either UNITCONV_eV_to_AU or SI::ATOMIC_UNIT_ENERGY for that purpose
+         *     -> use either sim.si.conv.ev2auEnergy() or sim.si.conv.joule2auEnergy() for that purpose
          *     - use `float_X` as the preferred data type
          *
          * example:
@@ -76,24 +76,24 @@ namespace picongpu
                     float_X,
                     18,
                     Argon,
-                    15.7596119 * UNITCONV_eV_to_AU,
-                    27.62967 * UNITCONV_eV_to_AU,
-                    40.735 * UNITCONV_eV_to_AU,
-                    59.58 * UNITCONV_eV_to_AU,
-                    74.84 * UNITCONV_eV_to_AU,
-                    91.290 * UNITCONV_eV_to_AU,
-                    124.41 * UNITCONV_eV_to_AU,
-                    143.4567 * UNITCONV_eV_to_AU,
-                    422.60 * UNITCONV_eV_to_AU,
-                    479.76 * UNITCONV_eV_to_AU,
-                    540.4 * UNITCONV_eV_to_AU,
-                    619.0 * UNITCONV_eV_to_AU,
-                    685.5 * UNITCONV_eV_to_AU,
-                    755.13 * UNITCONV_eV_to_AU,
-                    855.5 * UNITCONV_eV_to_AU,
-                    918.375 * UNITCONV_eV_to_AU,
-                    4120.6657 * UNITCONV_eV_to_AU,
-                    4426.2229 * UNITCONV_eV_to_AU);
+                    sim.si.conv.ev2auEnergy(15.7596119),
+                    sim.si.conv.ev2auEnergy(27.62967),
+                    sim.si.conv.ev2auEnergy(40.735),
+                    sim.si.conv.ev2auEnergy(59.58),
+                    sim.si.conv.ev2auEnergy(74.84),
+                    sim.si.conv.ev2auEnergy(91.290),
+                    sim.si.conv.ev2auEnergy(124.41),
+                    sim.si.conv.ev2auEnergy(143.4567),
+                    sim.si.conv.ev2auEnergy(422.60),
+                    sim.si.conv.ev2auEnergy(479.76),
+                    sim.si.conv.ev2auEnergy(540.4),
+                    sim.si.conv.ev2auEnergy(619.0),
+                    sim.si.conv.ev2auEnergy(685.5),
+                    sim.si.conv.ev2auEnergy(755.13),
+                    sim.si.conv.ev2auEnergy(855.5),
+                    sim.si.conv.ev2auEnergy(918.375),
+                    sim.si.conv.ev2auEnergy(4120.6657),
+                    sim.si.conv.ev2auEnergy(4426.2229));
 
             } // namespace AU
         } // namespace energies