LOW TEMPERATURE $(\sim 20K)$ INTRAMOLECULAR ENERGY TRANSFER IN GAS PHASE EVIDENCED BY LUMINESCENCE OF $N_{2}, {N^{+}}_{2}$, AND CN.

Abstract

Gas phase luminescence spectra of $N_{2} (1^{+}-system), (N^{+}}_{2} (1^{+}-system)$, and CN (Red system) in the temperature range 180K - 20K have been studied in the frame of original experimental approach [1] consisting in injection of helium gas jet containing the exposed to HF discharge admixtures under investigation into the cryostat with superfluid helium $(T \sim 1.5K)$. At low temperatures together with strong suppression of rotational structure the dramatic changes in the vibronic bands intensity (some bands almost completely disappear) are observed [2]. For all vibrational levels from which emission is temperature sensitive there are quasiresonant $(\Delta {\rm E} < 100 cm^{-1})$ vibrational levels belonging to another electronic states of the same species. So the effect has been explained by effective energy transfer between the electronic states induced by collisions with cold helium atoms $([He] \sim 10^{-19} cm^{-3})$. The emission bands intensity is determined by mutual disposition of the interacting levels. Its decrease or increase depend on whether exothermic or endothermic, respectively, transition from emitting level to neighboring one. Observed phenomena provide new opportunities for accurate testing the mutual disposition of different electronic states in diatomics as well as for study of intersystem collisional induced processes.