Anti-resonance in naphthalene and anthracene, determined from highly resolved and polarized pre-resonance Raman excitation spectra

Abstract

Polarized Raman excitation spectra of various Raman lines in naphthalene and anthracene were measured with high resolution in the pre-resonance region of the lowest allowed electronic transitions. The investigated non-totally symmetric modes exhibit a prominent anti-resonance, but show no polarization dispersion, while the investigated symmetric modes show a hidden anti-resonance, i.e. an anti-resonance with no minimum in the excitation profile, but with a deviating wavenumber behaviour, followed by a strong polarization dispersion. The experimental data are interpreted in terms of a vibronic model using up to three electronic states. It is shown that only when both linearly polarized excitation spectra are measured is it possible to distinguish uniquely between the different scattering models.

Survival of molecular information under surfaced‐enhanced resonance Raman (SERRS) conditions

“…In some cases, the REP does not show a minimum but only a wavenumber dependence, which is different from the typical preresonance behavior. As demonstrated by Ehland et al, [36] this kind of antiresonance may be clearly revealed in the depolarization ratio. Although different molecular sources of antiresonance exist, depending on the molecular properties, antiresonance is basically due to the destructive interference between the various contributions to the Raman tensor, each of which is determined by a state tensor and the corresponding complex energy denominator.…”

“…Antiresonance in naphthalene and anthracene, belonging to the point group D 2h , has been studied experimentally by Ito and Suzuka [33] ; Schmid et al [34] ; Ohta and Ito [35] ; Ehland et al [36] and theoretically by Hassing, [37] and Zheng and Wei. [38] The intensity of the measured REP for both symmetric and asymmetric modes will normally increase when the excitation wavenumber is approaching an electronic transition.…”

“…[36] to fit the experimental REP and DPR. In general, several electronic states may influence the pre-resonance data; in many cases, however, the antiresonance in the REP can be explained by incorporating only a few states in the model.…”

“…When considering the same scenario for an asymmetric vibration, it follows from the results obtained from Refs [33,36,37] that the experimental REP can be fitted by using a model based on the two electronic states used above. This model, however, predicts a strong dispersion of the DPR in the region of the antiresonance, which is not observed experimentally.…”

Theoretical Study of Doubly Resonant Sum-Frequency Vibrational Spectroscopy for 1,1′-Bi-2-naphthol Molecules on Water Surface

“…10,14 Both surface doubly resonant IR-UV SFVS and SFVS off electronic resonance are capable of determining the molecule orientation at interfaces, but their molecular origins are different: SFVS off electronic resonance is related to the nonresonant Raman polarizability, while doubly resonant IR-UV SFVS is related to the resonant Raman polarizability. Theoretically, two different terms are considered in calculating the Raman polarizability: 16 Raman A term originates from the Franck−Condon progression that depends on the displacements of potential energy surfaces between the ground and excited electronic states, the electric transition dipole moments, and the line width of the resonant excited state; Raman B term is a Herzberg−Teller term that depends on the electric transition dipole moments and their derivatives. Both Raman A and B terms contribute to resonant Raman while only Raman B term contributes to nonresonant Raman.…”