1 degree kelvin= 8.621738 X10^-5  eV
                             = 0.0862          meV
                             = 0.695            cm^-1

     1 a.u =   27.211396 eV   =  219 474.63 05 cm^-1
     1 Ry =   13.6057      eV
     1 eV  =  8065.54   cm^-1
     1 eV= 11,600  degrees Kelvin

   1 meV = 8.065 cm^-1

1 Kcal/mol= 0.0434 eV = 43.4 meV

Photon momentum    k= 2.7 x10^-4 E (eV)

Atomic units:
in time = a /v₀ = 2.41 x10 ^-17 sec
in frequency =     4.13 x10¹⁶ Hz
in electric field=  5.14 x 10 ⁹ V/cm
 

Oscillator strength and transition rates
  A= 2*(E²/c³) f   (4.13 x10¹⁶)    1/sec
   where E is in a.u. , c=137.03604 and f  is the oscillator strength for emission

Laser intensity and field strength
  1 a.u. in E= 5x10⁹   V/cm
  1 a.u. in intensity= 3.5 x10¹⁶ (w/cm²)
   I  (watts/cm²)= 1.33 x10^-3 E²  (V/cm²)
 
 
 
 

Energy difference between D(1s) and H(1s) is 3.7 meV, or 1.36 X10^{-4   a.u.}

mass of proton in a.u. is         1836.152701
mass of deuteron in a.u. is    3670.483014
mass of neutron in a.u.   is    1838.683662