Rotational motion compensates the energy defect in near-resonant vibration vibration energy transfer:: A state-to-state study of NO(v)+N2O

lack of understanding of the factors that compensate energy defects in near resonant V-V energy transfer constrains our ability to accurately predict resonance widths and, thus, the overall importance of such processes. We have carried out one of the first truly state-to-state measurements of near resonant V-V energy transfer under single collision conditions, employing the crossed molecular beams, stimulated emission pumping technique. We have varied the energy defect Delta E for the process: NO X (2)Pi(upsilon-1)+N2O(0,0,1), by changing the prepared vibrational state from upsilon=22 (Delta E= + 14 cm(-1)) to upsilon = 21 (Delta E= -18 cm(-1)) to upsilon=20 (Delta E= -49 cm(-1)). Changes in the energy transfer efficiencies and rotational distributions of vibrationally inelastically scattered NO with energy defect both strongly suggest that molecular rotation (both of NO and N2O) is responsible for compensating the energy defect. Furthermore it appears that relative translation is ineffective in compensating the energy defect. A Delta J(NO)similar to Delta J(N2O) approximation also appears valid. (C) 1998 American Institute of Physics.