Characteristics and relaxation dynamics of van der Waals complexes between p-difluorobenzene and Ne

摘要

Characteristics of the single and double Ne van der Waals complexes of p-difluorobenzene (pDFB) have been explored with ultraviolet fluorescence excitation and dispersed fluorescence spectroscopy.Eight S_1-S_0 fluorescence excitation bands involving six ring modes of pDFB-Ne and two bands of pDFB-Ne_2 have been identified.Band assignments are confirmed by dispersed fluorescence from the pumped band.Shifts of the complex bands from the analogous monomer bands are generally 4 cm~(-1) to the red for pDFB-Ne and 8 cm~(-1) for pDFB-Ne_2.None of the observed ring modes is significantly perturbed by complexation in either the S_1 or S_0 states.The pDFB-Ne S_1 van der Waals binding energy D'_0 <=120cm~(-1) is inferred from fluorescence band assignments with D'_0 - D_0" = 4 cm~(-1).Vibrational predissociation of pDFB-Ne to produce the S_1 monomer is observed after pumping several levels,but the dissociation process is generally slow compared to fluorescence decay of the complex.Dissociation of the double complex pDFB-Ne_2 occurs from one level to produce S_1 pDFB-Ne in its zero point level.Comparisons are made with the relaxation dynamics of the S] complexes pDFB-Ar and pDFB-N_2.