Nonadiabatic effects in the lowest 0(+)(P-3) ion-pair states of CIF

Nonadiabatic calculations of vibrational energies and wave functions are ca rried out for the E(0(+), P-3(2)) and f(0(+), P-3(0)) ion-pair states of th e ClF molecule. It is shown that strong radial coupling between these 0(+) states is caused by a significant variation of their (3)Sigma (-) and (3)Pi Lambda -S contributions with internuclear distance and results in vibratio nal energy shifts as well as changes in the corresponding adiabatic vibrati onal wave functions. Both resonance and nonresonance interactions between v ibronic levels of these two adiabatic states are found to be important, but significant mixing of the adiabatic wave functions can occur only for the nearly resonant levels located around f,v=3; E,v=7 and f,v=8; E,v=13. Nonad iabatic interactions are found to be responsible for the appearance of long -wavelength maxima in the f,v=3,4 emission spectra that was the subject of the discrepancy between theoretical and experimental data discussed in the previous paper [A. B. Alekseyev, H.-P. Liebermann, R. J. Buenker, and D. B. Kokh, J. Chem. Phys. 112, 2274 (2000)]. Inclusion of nonadiabatic effects leads to notably better agreement between the calculated and measured bound -free emission spectra. (C) 2001 American Institute of Physics.