Nuclear motion on the orbitally degenerate electronic ground state of fully deuterated triatomic hydrogen

Nuclear motion in the vicinity of conical intersections of the degenerate electronic ground state of fully deuterated triatomic hydrogen, D3, is investigated with the aid of a time-dependent wavepacket approach in hyperspherical coordinates. Vibronic energy level spectra and the eigenfunctions are examined by including, for example, (1) geometric phase (GP) correction, (2) diagonal Born-Huang (BH) correction, and (3) both GP and BH corrections to the Born-Oppenheimer adiabatic Hamiltonian and finally by considering the nonadiabatic coupling between the two electronic surfaces explicitly. It emerges from this study that inclusion of both the GP and BH corrections is insufficient to explain the spectral features observed in the experiment. The latter are recovered by considering the complete two-states coupled Hamiltonian only. This study shows that both the GP and BH corrections constitute a minor part of the surface coupling effects, in particular, on the dynamics of the upper adiabatic sheet. Most importantly, we add that the experimental signature of the GP effect appears only in the observed shift of the eigenlevels of the electronic state when compared to those obtained from a completely Born-Oppenheimer Hamiltonian. The detail fine structure of the observed band of the electronic state is shaped by the off-diagonal derivative coupling elements of the nonadiabatic coupling operator

Theoretical study of ClH₂⁻ electron detachment spectroscopy revisited

Electron detachment spectroscopy of ClH2− and ClD2− is revisited in this paper. Franck–Condon transition from the ground vibrational level of the electronic ground state of the anion to the coupled electronic manifold of the neutral species is investigated by a time-dependent wave packet (WP) approach. Rich vibronic structures due to Cl…H2 continuum states at higher energies appeared in the photodetachment band in our previous study [Chem. Phys. Lett. 394 (2004) 207] are eliminated on improving the representation of the anionic wavefunction and the WP propagation algorithm. The theoretical findings are compared with the available experimental and theoretical results

Quantum nonadiabatic dynamics of hydrogen exchange reactions

In continuation of our earlier effort to understand the nonadiabatic coupling effects in the prototypical H + H₂ exchange reaction [Jayachander Rao et al. Chem. Phys. 333 (2007) 135], we present here further quantum dynamical investigations on its isotopic variants. The present work also corrects a technical scaling error occurred in our previous studies on the H + HD reaction. Initial state-selected total reaction cross sections and Boltzmann averaged thermal rate constants are calculated with the aid of a time-dependent wave packet approach employing the double many body expansion potential energy surfaces of the system. The theoretical results are compared with the experimental and other theoretical data whenever available. The results re-establish our earlier conclusion, on a more general perspective, that the electronic nonadiabatic effects are negligible on the important quantum dynamical observables of these reactive systems reported here

A comparative account of quantum dynamics of the H+ + H2 reaction at low temperature on two different potential energy surfaces

Rotationally resolved reaction probabilities, integral cross sections, and rate constant for the H+ + H2 (v = 0, j = 0 or 1) → H2 (v′ = 0, j′) + H+ reaction are calculated using a time-independent quantum mechanical method and the potential energy surface of Kamisaka et al. [J. Chem. Phys. 116, 654 (2002)] (say KBNN PES). All partial wave contributions of the total angular momentum, J, are included to obtain converged cross sections at low collision energies and rate constants at low temperatures. In order to test the accuracy of the KBNN PES, the results obtained here are compared with those obtained in our earlier work [P. Honvault et al., Phys. Rev. Lett. 107, 023201 (2011)] using the accurate potential energy surface of Velilla et al. [J. Chem. Phys. 129, 084307 (2008)]. Integral cross sections and rate constants obtained on the two potential energy surfaces considered here show remarkable differences in terms of magnitude and dependence on collision energy (or temperature) which can be attributed to the differences observed in the topography of the surfaces near to the entrance channel. This clearly shows the inadequacy of the KBNN PES for calculations at low collision energies

Quantum dynamics of H+LiH⁺ reaction on its electronic ground state

State specific dynamics of the H + LiH+ reaction is theoretically investigated on its electronic ground potential energy surface employing a time-dependent wave packet approach. Channel specific integral reaction cross-sections and thermal rate constants are reported. Impact of the low-energy collision-induced dissociation channel on the reactive dynamics is discussed

Quantum dynamics of <SUP>16</SUP>O + <SUP>36</SUP>O<SUB>2</SUB> and <SUP>18</SUP>O + <SUP>32</SUP>O<SUB>2</SUB> exchange reactions

We present quantum dynamical investigations of <SUP>16</SUP>O + <SUP>36</SUP>O<SUB>2</SUB> and <SUP>18</SUP>O + <SUP>32</SUP>O<SUB>2</SUB> exchange reactions using a time-independent quantum mechanical method and an accurate global potential energy surface of ozone [Dawes et al., J. Chem. Phys. 135, 081102 (2011)]. Initial state-selected integral cross sections, rate constants, and Boltzmann averaged thermal rate constants are obtained and compared with earlier experimental and theoretical results. The computed thermal rate constants for the oxygen exchange reactions exhibit a negative temperature dependence, as found experimentally. They are in better agreement with the experiments than the previous studies on the same reactions

Time-dependent quantum wave packet dynamics of the C + OH reaction on the excited electronic state

Quantum state-selected dynamics of C(3P) + OH (X2Π) → CO(a3Π) + H (2S) reaction on its first excited electronic potential energy surface (12A″) is examined here using a time-dependent wave packet propagation approach. All partial wave contributions for the total angular momentum, J = 0−95, are included to obtain the converged cross sections and initial state-selected rate constants in the temperature range of 10−500 K. The reaction probability, as a function of collision energy, exhibits dense oscillatory structures owing to the formation of resonances during collision. These resonance structures also persist in reaction cross sections. The effect of reagent rotational and vibrational excitation on the dynamical attributes is examined and discussed. Reagent rotational excitation decreases the reactivity whereas, vibrational excitation of the reagent has minor effects on the reactivity. The results presented here are in good accord with those obtained using the time-independent quantum mechanical and quasi-classical trajectory methods

Time-dependent quantum wave packet dynamics of S + OH reaction on its electronic ground state

Initial state-selected dynamics of the S(³P) + OH (X²Π) → SO (X³Σ^–) + H (²S) reaction on its electronic ground potential energy surface (X̃²A″) is investigated here by a time-dependent wave packet propagation (TDWP) approach. Total reaction probabilities for the three-body rotational angular momentum up to <i>J</i> = 138 are calculated to obtain converged integral reaction cross sections and state-specific rate constants employing the centrifugal sudden (CS) approximation. The convergence of the latter quantities is checked by varying all parameters used in the numerical calculations. The cross section and rate constant results are compared with those available in the literature, calculated with the aid of the quasi-classical trajectory method on the same potential energy surface. Reaction probabilities obtained with the TDWP approach exhibit dense oscillatory structures, implying formation of a metastable quasi-bound complex during the collision process. The effect of rotational and vibrational excitations of reagent OH on the dynamical attributes is also examined. While the rotational excitation of reagent OH decreases the reactivity, its vibrational excitation enhances the same

Time-dependent quantum wave packet dynamics of the C + OH reaction on the excited electronic state

Quantum state-selected dynamics of C(3P) + OH (X2Π) → CO(a3Π) + H (2S) reaction on its first excited electronic potential energy surface (12A″) is examined here using a time-dependent wave packet propagation approach. All partial wave contributions for the total angular momentum, J = 0−95, are included to obtain the converged cross sections and initial state-selected rate constants in the temperature range of 10−500 K. The reaction probability, as a function of collision energy, exhibits dense oscillatory structures owing to the formation of resonances during collision. These resonance structures also persist in reaction cross sections. The effect of reagent rotational and vibrational excitation on the dynamical attributes is examined and discussed. Reagent rotational excitation decreases the reactivity whereas, vibrational excitation of the reagent has minor effects on the reactivity. The results presented here are in good accord with those obtained using the time-independent quantum mechanical and quasi-classical trajectory methods