Spin-Orbit and Vibrational Relaxation Rate Constants and Radiative Lifetimes for v'=0-5 Levels of PF(A~3II_(0,1,2) Molecules

摘要

One-photo laser excitation of PF(X~3Σ~-) molecules generated in a discharge-flow reactor was used to prepare PF(A~3Π_(0,1,2) molecules in selected vibrational and spin-orbit levels. The radiative lifetimes, collisional relaxational mechanisms, and state-to-state rate constants for spin-orbit and vibrational relaxation were assigned in He and Ar bath gas for v'=0-5 levels at 300 K. The radiative lifetimes, which are independent of the spin-orbit quantum number, Ω, decrease from 4.2 to 1.8 μs for v'=0-5. the spin-orbit relaxation mechanisms in He and in Ar are independent of v' level to within the experimental uncertainty. However, the actual rate constants for spin-orbit relaxation are different in He and Ar. In He the rate constant for ΔΩ=-2 change are 2-fold larger than those for ΔΩ=-1, whereas in Ar the order is reversed and the rate constants for ΔΩ=-1 change are larger than the rate constant for ΔΩ=-2 change. Furthermore, in Ar the rate constant for ΔΩ=-1 transfer is much larger for ~3Π_1→~3Π_0 than for ~3Π_2→~3Π_1. Although the vibrational relaxation mechanisms in He and Ar have different degrees of involvement of the spin-orbit states, the overall vibrational deactivation rate constants are similar in He and Ar and both increase with vibrational level.