Collision Energy Transfer And Reaction Dynamics Of K,Cs By Hydrogen

(1)The vibrational energy transfer from vibrational levels of KH( X1Σ+ ,v=0-5) bycollision with H2 is determined using the integrated time-resolved LIF in a five-armcrossed heat-pipe oven. K-H2 mixture is irradiated with pulses of 728.7 nm radiation ,populating 6S1/2 state by two-photon absorption.The vibrational levels ofKH( X1Σ+ ,v=0-5) generated in the reaction of K(6S) and H2 are selectively detectedby the laser-induced fluorescence(LIF) technique. The nascent primitive quantum statedistributions of the KH are obtained when the delay time between the pump and probelaser are 20ns.The time-resolved LIF-excitedA1Σ+â†'X1Σ+ system in the presence ofH2 has been recorded with the delay time from 0 to 100μs .The experiments show thatenergy transfer from KH( X 1Σ+ , v≠2 ) to v=2 is surprisingly efficient compared tothat of other vibrational levels studied here.From the rate equations and the integratedprofiles method(IPM) plots ,the rate coefficients for relaxation of KH( X1Σ+ ,v=3-5) bycollisions with H2 are 9.6×10-13cm3s-1 for v=5â†'v=4 and 2.31×10-13cm3s-1 forv=4â†'v=3 and the diffusion rate of v=4 is 1.5×105s-1。(2)By using a pump-probe technique, the nascent rotational and vibrational statedistributions of CsH are obtained in the Cs(62D,72D) plus H2 reaction. The nascentCsH molecules are found to populate the lowest two vibrational (v′′=0 and 1) levels ofthe ground electronic state. By comparing the spectral intensities of the CsH actionspectra with those of pertinent Cs atomic fluorescence excitation spectra, the relativereactivity with H2 is in an order of 62D3/2>62D5/2>72D3/2>72D5/2. The rotationaltemperatures are found to be slightly below the cell temperature. The relativefractions(,,) 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 the62D3/2,62D5/2,72D3/2 and 72D5/2,respectively.The major available energy is released astranslation. These results support that the reaction mechanism of Cs(62D,72D) plus H2 is primarily a collinear abstraction and not an insertion.