Vibrational state distributions and absolute excitation efficiencies for T-V transfer collisions of NO and CO with H atoms produced by excimer laser photolysis

Translation-to-vibration energy transfer from fast H atoms to NO and CO is studied by the excimer laser photolysis/infrared fluorescence method. The excited vibrational state distribution in NO resulting from collisions with H atoms at 2.3 eV initial translational energy is 0.55 +- 0.03, 0.24 +- 0.03, 0.07 +- 0.03, 0.05 +- 0.03, 0.04 +- 0.02, 0.03 +- 0.02, and 0.01 +- 0.02 for v = 1--7, respectively. The distribution is similar to that previously reported for H+CO collisions at the same energy [C. A. Wight and S. R. Leone, J. Chem. Phys. 78, 4875 (1983)]. However, the absolute T-V transfer efficiency for H+CO is a strong function of initial energy, increasing from 7% at 0.95 eV to 28% at 3.1 eV, whereas the efficiency for H+NO is essentially constant at 14% over the same range of initial energies. This qualitatively different behavior is not expected from simple models of T-V energy transfer, but may be attributed to differences in the attractive regions of the potential energy surfaces of the HNO and HCO transient species