Collisional energy transfer probabilities of highly excited molecules from KCSI.III.Azulene:P(E',E) and moments of energy transfer for energies up to 40000 cm~(-1) via self-calibrating experiments

摘要

Complete experimental transition probability density functions P(E',E) have been determined for collisions between highly vibrationally excited azulene and several bath gases over a wide energy range.This was achieved by applying 2-color "kinetically controlled selective ionization (KCSI)"[U.Hold,T.Lenzer,K.Luther,K.Reihs,and A.C.Symonds,J.Chem.Phys.112,4076 (2000)].The results are "self-calibrating,"i.e.,independent of any empirical calibration curve,as usually needed in traditional energy transfer experiments like time0-resolved ultraviolet absorption or infrared fluorescence.The complete data set can be described by our recently introduced monoexponential 3-parameter P(E',E) form with a parametric exponent Y in the argument,P(E',E)~propor.to exp[-(E-E')/(C_0+C_1 centre dot E)}~Y].For small colliders (helium,argon,xenon,N_2,and CO_2) the P(E',E) show increased amplitudes in th wings compared to a monoexponential form (Y < 1).For larger colliders,the wings of P(E',E) have an even smaller amplitude (Y>1) than that provided by a monoexponential.Approximate simulations show that the wings of P(3',E) at amplitudes <1X10~(-6) (cm~(-1))~(-1) have a nearly negligible influence on the population distributions and the net energy transfr.All optimized P(E',E) representations exhibit a linear energy dependence of the collision parameter alpha_1(E)=C_0+C_1 centre dot E,which also results in an (approximately) linear dependence of and ~1/2.The energy transfer parameters presented in this study have benchmark character in certainty and accuracy,e.g.,wiht only 2%-5% uncertainty for our data below 25 000 cm~(-1).Deviations of previously reported first moment data from ultraviolet absorption and infrared fluorescence measurements can be traced back to either the influence of azulene self-collisions or well-known uncertainties in calibration curves.