.. index:: physconst
.. _`apdx:physconst`:

Physical Constants
==================

.. table:: Physical constants in |PSIfour|

   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   | Label                   | Value                | Description                                                                                          |
   +=========================+======================+======================================================================================================+
   |                   psi_h | 6.62606896E-34       |  The Planck constant (Js)                                                                            |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |                   psi_c | 2.99792458E8         |  Speed of light (ms$^{-1}$)                                                                          |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |                  psi_kb | 1.3806504E-23        |  The Boltzmann constant (JK$^{-1}$)                                                                  |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |                   psi_R | 8.314472             |  Universal gas constant (JK$^{-1}$mol$^{-1}$)                                                        |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |      psi_bohr2angstroms | 0.52917720859        |  Bohr to Angstroms conversion factor                                                                 |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |              psi_bohr2m | 0.52917720859E-10    |  Bohr to meters conversion factor                                                                    |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |             psi_bohr2cm | 0.52917720859E-8     |  Bohr to centimeters conversion factor                                                               |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |               psi_amu2g | 1.660538782E-24      |  Atomic mass units to grams conversion factor                                                        |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |              psi_amu2kg | 1.660538782E-27      |  Atomic mass units to kg conversion factor                                                           |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |              psi_au2amu | 5.485799097E-4       |  Atomic units (m$@@e$) to atomic mass units conversion factor                                        |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |           psi_hartree2J | 4.359744E-18         |  Hartree to joule conversion factor                                                                  |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |          psi_hartree2aJ | 4.359744             |  Hartree to attojoule (10$^{-18}$J) conversion factor                                                |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |               psi_cal2J | 4.184                |  Calorie to joule conversion factor                                                                  |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |        psi_dipmom_au2si | 8.47835281E-30       |  Atomic units to SI units (Cm) conversion factor for dipoles                                         |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |     psi_dipmom_au2debye | 2.54174623           |  Atomic units to Debye conversion factor for dipoles                                                 |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |     psi_dipmom_debye2si | 3.335640952E-30      |  Debye to SI units (Cm) conversion factor for dipoles                                                |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |                psi_c_au | 137.035999679        |  Speed of light in atomic units                                                                      |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |          psi_hartree2ev | 27.21138             |  Hartree to eV conversion factor                                                                     |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   | psi_hartree2wavenumbers | 219474.6             |  Hartree to cm$^{-1}$ conversion factor                                                              |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |     psi_hartree2kcalmol | 627.5095             |  Hartree to kcal mol$^{-1}$ conversion factor                                                        |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |       psi_hartree2kJmol | 2625.500             |  Hartree to kilojoule mol$^{-1}$ conversion factor                                                   |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |         psi_hartree2MHz | 6.579684E9           |  Hartree to MHz conversion factor                                                                    |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   | psi_kcalmol2wavenumbers | 349.7551             |  kcal mol$^{-1}$ to cm$^{-1}$ conversion factor                                                      |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |                  psi_e0 | 8.854187817E-12      |  Vacuum permittivity (Fm$^{-1}$)                                                                     |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |                  psi_na | 6.02214179E23        |  Avagadro's number                                                                                   |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+
   |                  psi_me | 9.10938215E-31       |  Electron rest mass (in kg)                                                                          |
   +-------------------------+----------------------+------------------------------------------------------------------------------------------------------+