Vibrational predissociation in S1 indole van der Waals clusters

Abstract

The excited state dynamics of the indole(Ar)1, indole(d1)(Ar)1, indole(Ar)2, and indole(CH4)1 van der Waals clusters have been investigated in a free jet expansion. Excited state vibrational frequencies were determined using multiphoton ionization and fluorescence excitation spectroscopy. Time resolved emission spectroscopic techniques were used to determine vibrational predissociation rates and product state distributions. All of the clusters were found to predissociate when excited with sufficient vibrational energy in the S1 state. The predissociation dynamics were found to be consistent with a serial model in which energy transfer from the indole skeletal modes to the van der Waals modes precedes the dissociation step. The density of van der Waals vibrational states was found to be the most important factor in determining the predissociation dynamics.

New assignments in the UV spectroscopy of the small benzene–argonn clusters: The effects of a structure-selective vibrational predissociation

“…This point was also invoked in a recent study on indole-Ar n , nϭ1 and 2. 31 The same theoretical considerations also account for the higher IVR rates in larger complexes due to an increased density of states. However, the larger relaxation rates of ͑2/0͒ and ͑2/1͒ clusters compared to those of species of larger size and hence of larger density of states ͓like ͑3/0͒, ͑3/1͒ and ͑4/0͔͒ suggests that the coupling matrix element might be much smaller in the latter species, in connection with their possible high symmetry, in particular C 3 for nϭ3.…”

Binding energies of carbazole⋅S van der Waals complexes (S=N2, CO, and CH4)

“…The D 0 (S 0 )ϭ668.6Ϯ15.1 cm Ϫ1 for carbazole•CH 4 is significantly higher than for the aniline•CH 4 complex, in agreement with the fact that carbazole is larger than aniline. By fluorescence measurements Outhouse and co-workers 33 determined an upper limit for the binding energy of indole•CH 4 as D 0 (S 0 )Ͻ682 cm Ϫ1 , which falls into the range determined for carbazole•CH 4 , D 0 (S 0 )ϭ668.6Ϯ15.1 cm Ϫ1 . Although indole and carbazole are structurally similar, carbazole is larger by one benzene ring and the binding energy must be larger than for indole•CH 4 .…”

“…vdW complexes with CH 4 were investigated by various groups. 5,8,27,32,33 Molecular beam studies on vibrational predissociation processes 27,29,33 also yielded limits for binding energies. The methane/graphite system has stimulated considerable experimental and theoretical work.…”

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

“…[43][44][45][46][47][48] In the modeling for pDFB-Ar and pDFB-N 2 , the relaxation dynamics from the initially pumped S 1 complex level always begins with IVR to isoenergetic levels comprised of a lower S 1 ring level in combination with an excited set of van der Waals modes. A number of applications of this model give evidence of its basic integrity.…”