In the present study, we have observed absorption, fluorescence excitation, and CP radical action spectra ofthe HCP molecule in the vicinity of the dissociation threshold to H(2S) + CP(X 2Σ+). In addition, we havemeasured the rotational distribution of the CP radical produced from certain single rovibronic levels of theparent HCP molecule. It is found that the CP radical action spectrum starts to appear at the point wherethe fluorescence intensity decreases suddenly. On the basis of the precise energetic consideration betweenthe parent and the product rovibronic energies, the dissociation energy of HCP to H(2S) + CP(X 2Σ+) isdetermined to be 41 662.3 ( 0.5 cm-1. The energy distribution in the predissociation is found to be basicallystatistical; however, the prominent preferences in the rotational distributions or nonstatistical distributionsare observed only when the vibronic energy of the parent level is smaller than the dissociation thresholdenergy. This preference is qualitatively interpreted by the inefficient energy transfer from the rotational to thevibrational degrees of freedom in the exit region of the X state potential energy surface. As a result, thedissociation proceeds along the linear H-C-P configuration, and this geometrical restriction makesnonstatistical rotational distribution of the CP radical.
展开▼
