Analysis of femtosecond stimulated Raman spectroscopy of excited-state evolution in bacteriorhodopsin
- Division of Physics and Applied Physics and Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore)
- Department of Chemistry, Duke University, Durham, North Carolina 27708-0354 (United States)
The dispersive lines observed in time-resolved femtosecond stimulated Raman spectroscopy (FSRS), using a pair of 809 nm, 3 ps Raman pump, and 840-960 nm ultrashort probe pulse, for the first 500 fs photoisomerization dynamics in the excited state of bacteriorhodopsin, BR* (S{sub 1}), created by a prior 500 nm, 35 fs actinic pump pulse, have previously been attributed to Raman initiated by nonlinear emission (RINE). We used four-wave mixing energy level diagrams to describe the FSRS process, which include RINE as a subset, and a 29-mode harmonic oscillator model for BR{sub 568} in the calculations. Our calculations showed that FSRS of BR{sup *} effectively occurs from the ground vibrational state of each of the observed 800-1800 cm{sup -1} modes of S{sub 1}. The lifetime on S{sub 1} determines the linewidth and decay of the dispersive lines, and is estimated to be {approx}600 fs, comparable to the stimulated emission decay time. The FSRS dipole couplings are from the ground vibrational state of S{sub 1} to high energy vibrational states on BR (S{sub 0}), and we place a fast decay lifetime of {approx}100 fs on S{sub 0} which can be attributed to the correlation function from the many unobserved low frequency modes. The FSRS dispersive lines are shown to be due to the inverse Raman scattering term with |0><1| vibrational coherence on the S{sub 1} surface, and are not due to RINE with vibrational coherence on the S{sub 0} surface. Our calculations show that the RINE process gives rise to broad featureless spectra.
- OSTI ID:
- 21559839
- Journal Information:
- Journal of Chemical Physics, Vol. 132, Issue 8; Other Information: DOI: 10.1063/1.3330818; (c) 2010 American Institute of Physics; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BROMINE IONS
CORRELATION FUNCTIONS
DECAY
DIPOLES
HARMONIC OSCILLATOR MODELS
HARMONIC OSCILLATORS
ISOMERIZATION
LIFETIME
PROBES
PROTEINS
PULSES
RAMAN EFFECT
RAMAN SPECTROSCOPY
STIMULATED EMISSION
TIME RESOLUTION
VIBRATIONAL STATES
CHARGED PARTICLES
CHEMICAL REACTIONS
EMISSION
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
FUNCTIONS
IONS
LASER SPECTROSCOPY
MATHEMATICAL MODELS
MULTIPOLES
ORGANIC COMPOUNDS
RESOLUTION
SPECTROSCOPY
TIMING PROPERTIES