EFFECT OF ISOTOPIC SUBSTITUTION ON V-V TRANSFER RATES BETWEEN CO TO CO, $N_{2}$ AND $O_{2}$

Author Institution: Laboratoire de Spectronomie Moleculaire, C.N.R.S., Universit\'{e} Pierre et Marie CurieV-V transfer rates from $^{12}CO(v = 1)$ to $^{14}N_{2}$, $^{15}N_{2}$, $^{13}CO$ and $O_{2}$ have been determined versus temperature, from 100 to 700$^\circ K$, using the laser fluorescence method. For the $^{12}CO- ^{13}CO$ and $^{12}CO- ^{15}N_{2}$ systems, the transfer rate decreases with temperature showing that long-range multi-polar forces have a preponderant effect on the transfer. For the less resonant systems $^{12}CO- ^{14}N_{2}$ and $^{12}CO-O_{2}$ the rate increases with temperature from $100^\circ K$ showing that repulsive forces have a dominant effect. For the two systems $^{12}CO- ^{14}N_{2} (\Delta \nu = - 187.5 cm^{-1})$ and $CO- ^{15}N_{2}(\Delta \nu = - 108.5 cm^{-1})$, the effect of the energy level gap $\Delta \nu$ between the colliding partners is dramatically demonstrated; at $100^\circ K$ , the ratio of these rates is as great as about 30; theoretical calculations explain these results. This set of experimental studies is a clear demonstration of the different interaction forces