The adiabatic and vertical ionization potentials of NH2 to the three lowest-lying states of NH2+

The adiabatic and vertical ionization potentials of the ground state ((X) o ver tilde(2)B(1)) of NH2 to the (X) over tilde(3)B(1), (a) over tilde(1)A(1 ) and (b) over tilde(1)B(1) states of NH2+ have been investigated systemati cally using ab initio electronic structure theory. The SCF, CASSCF, CISD, C ASSCF-SOCI, CCSD and CCSD(T) levels of theory with four basis sets have bee n employed to predict energy differences. The adiabatic and vertical ioniza tion potentials of the ground state of NH2 to the (X) over tilde(3)B(1) Sta te of NH2+ are determined to be 255.8 kcal/mol (11.09 eV, 89470 cm(-1)) and 277.1 kcal/mol (12.01 eV, 96900 cm(-1)), respectively, which are in excell ent agreement with the experimental values of 256.9 kcal/mol (11.14 eV, 898 50 cm(-1)) and 276.7 kcal/mol (12.00 eV, 96 790 cm(-1)). The theoretical ad iabatic and vertical ionization potentials to the (a) over tilde(1)A(1) sta te of NH2+ are evaluated to be 285.7 kcal/mol (12.39 eV, 99910 cm(-1)) and 287.3 kcal/mol (12.46 eV, 100480 cm(-1)), respectively, which are also in g ood agreement with the experimental values of 287.0 kcal/mol (12.445 eV, 10 0 380 cm(-1)) and 287.1 kcal/mol (12.45 eV, 100 420 cm(-1)). Finally the ad iabatic and vertical ionization potentials to the (b) over tilde B-1 state of NH2+ are predicted to be 298.1 kcal/mol (12.93 eV, 104270 cm(-1)) and 32 4.8 kcal/mol (14.09 eV, 113 600 cm(-1)), respectively. (C) 1999 Elsevier Sc ience B.V. AU rights reserved.