TY - JOUR
T1 - Femtosecond spectroscopy of ultrafast nonadiabatic excited-state dynamics on the basis of ab initio potential-energy surfaces
T2 - The S2 state of pyrazine
AU - Stock, Gerhard
AU - Domcke, Wolfgang
PY - 1993
Y1 - 1993
N2 - A theoretical description of femtosecond time-resolved optical spectroscopy of isolated polyatomic molecules is outlined. Our ultimate goal is the characterization of the system response on a microscopic level, that is, time-dependent quantum dynamics. Employing a simplified model Hamiltonian which includes the most relevant electronic states and vibrational modes, the intramolecular quantum dynamics is treated numerically exactly. The model Hamiltonian is constructed, via a Taylor expansion in terms of ground-state normal coordinates, from ab initio potential-energy surfaces. Additional phase relaxation effects (optical pure dephasing) due to weakly coupled modes have been included in a phenomenological manner using the density-matrix formalism. The radiation-matter interaction, derived from ab initio transition-dipole-moment functions, is treated in perturbation theory (up to third order for the polarization). The implementation of this approach is demonstrated for the S2(ππ*) state of pyrazine, which is strongly vibronically coupled to the lower-lying S1(nπ*) state. Basic aspects of ultrafast non-Born-Oppenheimer dynamics on multidimensional conically intersecting potential-energy surfaces and its detection by femtosecond pump-probe spectroscopy are discussed.
AB - A theoretical description of femtosecond time-resolved optical spectroscopy of isolated polyatomic molecules is outlined. Our ultimate goal is the characterization of the system response on a microscopic level, that is, time-dependent quantum dynamics. Employing a simplified model Hamiltonian which includes the most relevant electronic states and vibrational modes, the intramolecular quantum dynamics is treated numerically exactly. The model Hamiltonian is constructed, via a Taylor expansion in terms of ground-state normal coordinates, from ab initio potential-energy surfaces. Additional phase relaxation effects (optical pure dephasing) due to weakly coupled modes have been included in a phenomenological manner using the density-matrix formalism. The radiation-matter interaction, derived from ab initio transition-dipole-moment functions, is treated in perturbation theory (up to third order for the polarization). The implementation of this approach is demonstrated for the S2(ππ*) state of pyrazine, which is strongly vibronically coupled to the lower-lying S1(nπ*) state. Basic aspects of ultrafast non-Born-Oppenheimer dynamics on multidimensional conically intersecting potential-energy surfaces and its detection by femtosecond pump-probe spectroscopy are discussed.
UR - http://www.scopus.com/inward/record.url?scp=0010873785&partnerID=8YFLogxK
U2 - 10.1021/j100150a004
DO - 10.1021/j100150a004
M3 - Article
AN - SCOPUS:0010873785
SN - 0022-3654
VL - 97
SP - 12466
EP - 12472
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
IS - 48
ER -