Analytical derivation of the critical internuclear distance for barrier suppression ionization in diatomic molecules

We present an analytical derivation of critical internuclear distances R-c and electric field strengths E-c for barrier suppression ionization in diat omic molecules. For those atoms obeying I-P, atom((q)) = qI(P,atom)((l)) (I -P,atom((q)) is the qth ionization potential), the critical distance is giv en by R-c = 3.7872/I-P,atom((l)). For the symmetric Coulomb explosion energ y E-Coul we derive E-Coul = 0. 2640qI(P,atom)((q)). In other words, as a "r ule of the thumb" the symmetric Coulomb explosion energy at the critical di stance is roughly q(2)/4 times the ionization potential of the neutral atom . For the case of nonequally charged nuclei arbitrarily accurate critical d istances and barrier heights are calculated (and summarized in a fit formul a) as a function of the nuclear charges and the critical field strength. He nce, the critical distance, the critical field strength, and the Coulomb ex plosion energy can again be expressed in terms of the ionization potential of the neutral atom.