oms are prepared in the 6D state by two-photon absorption.CsH(X1∑+,v"=0)is generated from the Cs(6D)+H2 reaction.By overtone excitation with a pulsed dye laser,highly vibrational states v">15 of CsH in its ground electronic state are obtained.A diode laser is used to probe either the prepared vibrational state or the collisionally populated states.The decay signal of the time-resolved fluorescence from the A1∑+(v)→X1∑+(v")transition is monitored.Based on the Ste-Volmer equation,the total rate coefficients for v"=15-22 are yielded.The time evolution and relative intensities of three related states,v",v"-1 and v"-2,made by the initially prepared v"state of CsH are measured.Rate coefficients of single-and double-quantum relaxation are obtained.These results show that single-quantum relaxation accounts for ≥50%of the total relaxation out of states v"=17-20.Multiquantum relaxation(△v≥2)makes major contribution(≥62%)to the vibrational relaxation at v"=21 and 22.A simple explanation is given.