The Raman and vibronic activity of intermolecular vibrations in aromatic-containing complexes and clusters

Journal Article · Mon Nov 14 23:00:00 EST 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.468102· OSTI ID:7094966

Maxton, P M; Schaeffer, M W; Ohline, S M; Kim, W; Venturo, V A; Felker, P M ^[1]

---

1. Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1569 (United States)

Theoretical and experimental results pertaining to the excitation of intermolecular vibrations in the Raman and vibronic spectra of aromatic-containing, weakly bound complexes and clusters are reported. The theoretical analysis of intermolecular Raman activity is based on the assumption that the polarizability tensor of a weakly bound species is given by the sum of the polarizability tensors of its constituent monomers. The analysis shows that the van der Waals bending fundamentals in aromatic--rare gas complexes may be expected to be strongly Raman active. More generally, it predicts strong Raman activity for intermolecular vibrations that involve the libration or internal rotation of monomer moieties having appreciable permanent polarizability anisotropies. The vibronic activity of intermolecular vibrations in aromatic-rare gas complexes is analyzed under the assumption that every vibronic band gains its strength from an aromatic-localized transition. It is found that intermolecular vibrational excitations can accompany aromatic-localized vibronic excitations by the usual Franck--Condon mechanism or by a mechanism dependent on the librational amplitude of the aromatic moiety during the course of the pertinent intermolecular vibration. The latter mechanism can impart appreciable intensity to bands that are forbidden by rigid-molecule symmetry selection rules. The applicability of such rules is therefore called into question. Finally, experimental spectra of intermolecular transitions, obtained by mass-selective, ionization-detected stimulated Raman spectroscopies, are reported for benzene--X (X=Ar, --Ar[sub 2], N[sub 2], HCl, CO[sub 2], and --fluorene), fluorobenzene--Ar and --Kr, aniline--Ar, and fluorene--Ar and --Ar[sub 2]. The results support the conclusions of the theoretical analyses and provide further evidence for the value of Raman methods in characterizing intermolecular vibrational level structures.

• DOE Contract Number: FG03-89ER14066
• OSTI ID: 7094966
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 101:10; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

664200* -- Spectra of Atoms & Molecules & their Interactions with Photons-- (1992-)
664500 -- Special Atoms & Molecules-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
AMINES
ANILINE
ARGON COMPLEXES
AROMATICS
BENZENE
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHLORINE COMPOUNDS
COMPLEXES
CONDENSED AROMATICS
COUPLING
ELECTRICAL PROPERTIES
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
FLUORENE
FRANCK-CONDON PRINCIPLE
HALOGEN COMPOUNDS
HYDROCARBONS
HYDROCHLORIC ACID
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INTERMOLECULAR FORCES
KRYPTON COMPLEXES
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POLARIZABILITY
RAMAN SPECTRA
SPECTRA
TENSORS
VAN DER WAALS FORCES
VIBRATIONAL STATES