Numbers and Conversions Useful in EPR
Free electron g value: ge = 2.0023193
Boltzmann Constant: k = 0.69504 cm-1
Calculating the g value from the frequency and magnetic field:
g = (h/µB) γ / B = 714.4775 γ[GHz] / B[G]
Converting a hyperfine constant A from Gauss (that is the splitting seen in a spectrum) to cm-1:
A [cm-1] = (µB / hc) · g · A [G] = 4.66863·10-5 · g · A [G]
Note that the g value to which an EPR line belongs must be used in the conversion.
Zero-Field Splitting parameters D, E and higher-rank parameters Bmn are often expressed in Gauss instead of cm-1. This is convenient because, for example, in a spin-triplet spectrum the distance in Gauss between the "parallel" lines equals 2D[G] if g is not too far from 2. The conversion is:
D [cm-1] = (ge · µB / hc) · D [G] = 9.34809·10-5 · D [G]
Coefficient appearing in calculation of the dipolar interaction between electrons with the distance given in Ångstroms:
µ0 µB2 / 4π = 0.43297 cm-1 · Å3
Some numbers useful in calculations involving the magnetic susceptibility
NµB2 = 5584.939 erg / Gauss
in formulas for magnetization
NµB2 = 0.26074 cm-1
for calculating the Temperature Independent Paramagnetism (TIP, Nα)
NµB2/3k = 0.1250486 cgs emu · K
appearing in the famous formula χ = (NµB2/3kT) · g2 · S(S+1)
See also:
