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

Abstract

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')</=120 cm(-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(1) complexes pDFB-Ar and pDFB-N(2).

Electronic spectroscopy of toluene–rare-gas clusters: The external heavy atom effect and vibrational predissociation

“…3,6,8,[17][18][19][20][21] The majority of these studies examine dispersed fluorescence spectra following the pumping of excited cluster levels, and assign lines to transitions originating from the cluster or from fragments of the dissociation. The VP dynamics of aromatic molecule-rare-gas clusters have received considerable attention.…”

Recoil energy distributions for dissociation of the van der Waals molecule p-difluorobenzene–Ar with 450–3000cm−1 excess energy

“…There is a gap in our knowledge of how the product vibrational, rotational, and translational distributions evolve as the destination vibrations progress from a sparse to high density regime. While various studies have examined the vibrational energy distribution within the aromatic product, [8][9][10][11][12][13][14][16][17][18][19][20][21][22][23][24][25][26] there has been no systematic study of the evolution in the translational or rotational product state distributions with increasing vibrational energy within the complex.…”

Rotational distributions following van der Waals molecule dissociation: Comparison between experiment and theory for benzene–Ar

“…The KelleyBernstein model 32 provides a means to calculate dissociation rates of vdW complexes and to understand and rationalize the behavior observed across a series of complexes. 33 It does not, however, comment on the distribution of energy within the products. The AM model offers the possibility of extending our insight into the dissociation process by providing a quantitative understanding of the partitioning between rotational and translational excitation for each final vibrational state of the product.…”

“…This approach was recently used to model VP rates in p-difluorobenzene-rare gas complexes. 33 Our focus is on the subsequent dissociation step and the rotational excitation that ensues. In this section we describe an extension of the "internal collision" model of VP in vdW complexes of diatomic molecules 8 to the polyatomic case.…”