reaction is important in understanding the production mechanisms of anionic molecules in interstellar environments. Herein, the rate coefficients for the H − + C 2 H 2 → H 2 + C 2 H − reaction were calculated using ring-polymer molecular dynamics (RPMD), classical molecular dynamics (MD), and quasi-classical trajectory (QCT) approaches on a newly developed ab initio potential energy surface (PES) in full dimensions. PES was constructed by fitting a large number of ab initio energy points and their gradients using the permutationally invariant polynomial basis set method. There was no barrier in the reaction coordinates, which was a collinear-dominated reaction, and the reaction proceeded exothermically. It is found that the fitted PES provides the appropriate thermal rate coefficients based on all RPMD, classical MD, and QCT simulations at higher temperatures. The evaluation of the rate coefficients at lower temperatures should be conducted carefully because the fitting of the PES associated with the long-range interaction should be further improved. The spatial distribution of the nucleus allows a more effective attraction between the reactants.

Photoelectron spectroscopy of a molecular anion is very useful for investigating the transition state and intermediate regions on the reactive potential energy surfaces of a neutral system. In this work, we theoretically analyzed the previously measured photoelectron spectrum of the formylmethylene anion, HCCHO − . We simulated the photoelectron spectra for both the singlet and triplet states using the semiclassical method with quantum nuclear densities and Franck−Condon factor calculations with harmonic vibrational analysis. We also performed real-time quantum dynamics calculations to elucidate the importance of the Wolff rearrangement process, which leads to the stable product ketene from the carbene intermediate on the neutral singlet potential energy surface.

We present the results of quantum dynamics calculations for analyzing the experimentally measured photoelectron spectra of the OH−·NH3 anion complex. Detachment of an excess electron of OH−·NH3 initially produces a...

The dissociative photodetachment dynamics of the oxalate anion, C2O4H− + hν → CO2 + HOCO + e−, were theoretically studied using the on-the-fly path-integral and ring-polymer molecular dynamics methods, which can account for nuclear quantum effects at the density-functional theory level in order to compare with the recent experimental study using photoelectron–photofragment coincidence spectroscopy. To reduce computational time, the force acting on each bead of ring-polymer was approximately calculated from the first and second derivatives of the potential energy at the centroid position of the nuclei beads. We find that the calculated photoelectron spectrum qualitatively reproduces the experimental spectrum and that nuclear quantum effects are playing a role in determining spectral widths. The calculated coincidence spectrum is found to reasonably reproduce the experimental spectrum, indicating that a relatively large energy is partitioned into the relative kinetic energy between the CO2 and HOCO fragments. This is because photodetachment of the parent anion leads to Franck–Condon transition to the repulsive region of the neutral potential energy surface. We also find that the dissociation dynamics are slightly different between the two isomers of the C2O4H− anion with closed- and open-form structures.