#define useful constants
ergperev=1.60217653e-12# ergs in one eV
kb=8.617330350e-5 # eV K
clight=2.99792458e10 # cm/s
me=0.5109989461e6 # electron mass eV
mp=938.272081358e6# proton mass eV
e2=1.4399764e-7 # (e charge)^2 (eV cm)
