Nonadiabatic decay dynamics of phthalide from the light‐absorbing S₃(ππ*) state‐resonance Raman spectroscopy and CASSCF study

Abstract

Conical intersection or curve‐crossing is well known to be an efficient dynamic funnel for nonadiabatic transition between two different potential energy surfaces in chemical dynamics. Tremendous efforts have been made in the direct experimental probing of conical intersection. However, the direct following‐up of the dynamic process initiated from the Franck–Condon (FC) region toward a curve‐crossing point is still challenging. With the aid of complete active space self‐consistent field calculations, the resonance Raman spectroscopy has been applied to face challenges. Herein, the nonadiabatic decay dynamics of phthalide initiated from the light‐absorbing S3(ππ*) state were studied. The UV and vibrational spectra were assigned with the aid of the density functional theory calculations and normal‐mode analysis. The minima of the six lowest electronic excited states (S1, S2, S3, T1, T2, and T3) and the corresponding minimum‐energy intersections were fully optimized at the complete active space self‐consistent field level. The B‐band resonance Raman spectra in acetonitrile were simulated by using the time‐dependent wave‐packet theory in a simple model to obtain the dimensionless normal‐mode displacements, and the results were compared with the relative changes of the geometric structural parameters between the curve‐crossing points and S0 so as to help determine the decay channels initiated from the FC region. Two nonadiabatic decay channels were discovered, and that one of these had not been previously observed. The results provided general insights into the ultrafast decay dynamics initiated from the FC region of the light‐absorbing excited state to the nearby conical intersection or curve‐crossing points for organic molecules in solution. Copyright © 2017 John Wiley & Sons, Ltd.

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…They deduced two nonadiabatic decay channels and one of these had not been previously observed. The results provided general insights into the ultrafast decay dynamics initiated from the Franck–Condon region of the light‐absorbing excited state to the nearby conical intersection or curve‐crossing points for organic molecules in solution …”

“…The results provided general insights into the ultrafast decay dynamics initiated from the Franck-Condon region of the light-absorbing excited state to the nearby conical intersection or curvecrossing points for organic molecules in solution. [120] 14 | ART AND ARCHAEOLOGY The use of Raman spectroscopy in Art and Archaeology provides an example of the growing application of Raman as a sensitive nondestructive technique that can be used not only in the laboratory under controlled conditions but also in the field with compact portable instrumentation that provides spectral measurements of materials in situ without removal of samples to a laboratory setting. An area of growth is the use of micro-Raman spectroscopy that combines Raman scattering with optical microscopy so that one can obtain Raman spectra from microscopic-sized specimens as well as their corresponding optical images.…”