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Energy Flow in Push–Pull Chromophores: Vibrational Dynamics in para ‐Nitroaniline
Author(s) -
Gunaratne Tissa,
Challa J. Reddy,
Simpson M. Cather
Publication year - 2005
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400288
Subject(s) - intersystem crossing , chromophore , internal conversion , chemistry , excitation , photoexcitation , spectroscopy , ultrashort pulse , photochemistry , wavelength , raman spectroscopy , molecular physics , atomic physics , materials science , laser , optics , excited state , spectral line , physics , singlet state , optoelectronics , quantum mechanics , astronomy
para ‐Nitroaniline (PNA) plays an essential role as the prototype model of push–pull chromophores. The nature and degree of participation of vibrational degrees of freedom in the charge‐transfer and internal‐conversion processes are current issues of great theoretical and practical importance. Ultrafast time‐resolved anti‐Stokes resonance Raman spectroscopy (TRARRS) experiments on PNA in dimethyl sulfoxide with three different excitation wavelengths were performed to probe these dynamical influences. The vibrational dynamics associated with S 0 were independent of incident wavelength, and this supports the picture that the S 1 dynamics are fast relative to the rate of intersystem crossing. The phenyl breathing mode ν 19 (860 cm −1 ) and the symmetric NO 2 stretch ν 29 (1310 cm −1 ) exhibited vibrational lifetimes in S 0 of 8.1 and 5.2 ps, respectively. No evidence for inhomogeneous broadening of the charge‐transfer band in the UV/Vis absorption spectrum was found.