Photochemistry of pyrrole: Time-dependent quantum wave-packet description of the dynamics at the 1 -S0 conical intersections
نویسندگان
چکیده
The photoinduced hydrogen-elimination reaction in pyrrole via the conical intersections of the two 1 * excited states with the electronic ground states B1 * -S0 and A2 * -S0 have been investigated by time-dependent quantum wave-packet calculations. Model potential-energy surfaces of reduced dimensionality have been constructed on the basis of accurate multireference ab initio electronic-structure calculations. For the B1-S0 conical intersection, the model includes the NH stretching coordinate as the tuning mode and the hydrogen out-of-plane bending coordinate as the coupling mode. For the A2-S0 conical intersection, the NH stretching coordinate and the screwing coordinate of the ring hydrogens are taken into account. The latter is the dominant coupling mode of this conical intersection. The electronic population-transfer processes at the conical intersections, the branching ratio between the dissociation channels, and their dependence on the initial preparation of the system have been investigated for pyrrole and deuterated pyrrole. It is shown that the excitation of the NH stretching mode strongly enhances the reaction rate, while the excitation of the coupling mode influences the branching ratio of different dissociation channels. The results suggest that laser control of the photodissociation of pyrrole via mode-specific vibrational excitation should be possible. The calculations provide insight into the microscopic details of ultrafast internal-conversion processes in pyrrole via hydrogen-detachment processes, which are aborted at the 1 -S0 conical intersections. These mechanisms are of relevance for the photostability of the building blocks of life e.g., the DNA bases . © 2005 American Institute of Physics. DOI: 10.1063/1.2049250
منابع مشابه
Photochemistry of hydrogen-bonded aromatic pairs: Quantum dynamical calculations for the pyrrole-pyridine complex.
The photochemical dynamics of the pyrrole-pyridine hydrogen-bonded complex has been investigated with computational methods. In this system, a highly polar charge-transfer state of (1)pipi* character drives the proton transfer from pyrrole to pyridine, leading to a conical intersection of S(1) and S(0) energy surfaces. A two-sheeted potential-energy surface including 39 in-plane nuclear degrees...
متن کاملPhotodissociation dynamics of pyrrole: evidence for mode specific dynamics from conical intersections.
The H and D atom elimination mechanisms in the photodissociation of jet cooled pyrrole and pyrrole-d1 have been studied by photofragment velocity map imaging. The molecules were excited to the 1 1A2 (pi sigma*) state at lambda = 243 nm and to the 1 1B2 (pi pi*) state at lambda = 217 nm. H/D atoms were detected by (2 + 1) resonance enhanced multiphoton ionization (REMPI) at lambda = 243 nm. The ...
متن کاملTime-resolved photoelectron spectra of CS2: dynamics at conical intersections.
We report results of the application of a fully ab initio approach for simulating time-resolved molecular-frame photoelectron angular distributions around conical intersections in CS2. The technique employs wave packet densities obtained with the multiple spawning method in conjunction with geometry- and energy-dependent photoionization matrix elements. The robust agreement of these results wit...
متن کاملNon-adiabatic dynamics close to conical intersections and the surface hopping perspective
Conical intersections play a major role in the current understanding of electronic de-excitation in polyatomic molecules, and thus in the description of photochemistry and photophysics of molecular systems. This article reviews aspects of the basic theory underlying the description of non-adiabatic transitions at conical intersections, with particular emphasis on the important case when the dyn...
متن کاملContrasting ring-opening propensities in UV-excited α-pyrone and coumarin.
The photoisomerisation dynamics following excitation to the S1 electronic state of two structurally related heterocyclic molecules, α-pyrone and coumarin, in acetonitrile solution have been probed by time-resolved vibrational absorption spectroscopy. Following irradiation at 310 nm, α-pyrone relaxes rapidly from its initially excited state, with a quantum yield for parent molecule reformation o...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2005