Collision-induced fine-structure transitions of Hg(6(3)P(1)-> 6(3)P(0)) with N-2 and CO. 2. Translational energy dependence

Translational energy dependences of relative cross sections for Hg(6(3)P(1) --> 6(3)P(0)) fine-structure changing collisions with N-2 and CO have been measured with a crossed-beam apparatus over the energy range between 800 a nd 3750 cm(-1). A negative energy dependence is obtained for Hg-CO, but a p ositive energy dependence is observed for Hg-N-2, with an energy threshold for appearance of Hg(6(3)P(0)) around 900 cm(-1). These results are explain ed using the characteristics of the intermolecular potentials for Hg-N-2 an d Hg-CO. The existence of the energy threshold around 900 cm(-1) for N-2 su ggests simultaneous vibrational excitation of N-2. The translational energy dependence has also been measured under beam-gas conditions over the energ y range between 450 and 3350 cm(-1). From a comparison with Hg(6(3)P(1) --> 6(3)P(0)) intramultiplet deactivation cross sections for HE-N-2 and Hg-CO obtained in gas cell experiments, absolute values of the cross sections for this intramultiplet transition are estimated as a function of the average translational energy under the beam-gas conditions. There is no clear thres hold for Hg-N2 in the beam-gas experiment and it is suggested that a higher rotational temperature of N-2 induces a shift of the energy threshold effe ctively lower.