Rotational and Vibrational State Distributions of CsH and Relative Reactivity in Reactions of Cs(6²D, 7²D) with H₂

By using a pump-probe technique, the nascent rotational and vibrational state distributions of CsH are obtained in the Cs(6²D,7²D) plus H₂ reaction. The nascent CsH molecules are found to populate the lowest two vibrational (ν'' = 0 and 1) levels of the ground electronic state. By comparing the spectral intensities of the CsH action spectra with those of pertinent Cs atomic fluorescence excitation spectra, the relative reactivity with H₂ is in an order of 6²D_3/2 > 6²D_5/2 > 7²D_3/2 > 7²D_5/2. The rotational temperatures are found to be slightly below the cell temperature. The relative fractions (⟨f_V⟩, ⟨f_R⟩, ⟨f_T⟩) of average energy disposal are derived as (0.2,0.12,0.68), (0.2,0.12,0.68), (0.07,0.04,0.89) and (0.07,0.04,0.89) for the 6²D_3/2, 6²D_5/2, 7²D_3/2 and 7²D_5/2, respectively. The major available energy is released as translation. These results support that the reaction mechanism of Cs(6²D,7²D) plus H₂ is primarily a collinear abstraction and not an insertion.