Quantum study of the CH$_3^+$ photodissociation in full dimension Neural Networks potential energy surfaces

TL;DR

This paper develops full-dimensional neural network potential energy surfaces for CH$_3^+$ and uses quantum wave packet methods to study its photodissociation, providing insights relevant to interstellar chemistry and astrochemical modeling.

Contribution

It introduces a neural network approach to accurately model the potential energy surfaces of CH$_3^+$ in full dimension, enabling detailed quantum dynamical studies of its photodissociation.

Findings

Photodissociation spectra suggest less destruction of CH$_3^+$ in astrochemical environments.

Neural network potentials enable efficient and accurate quantum calculations.

Results impact astrochemical models of interstellar regions like the Orion Bar.

Abstract

CH$_3^+$, a cornerstone intermediate in interstellar chemistry, has recently been detected for the first time by the James Webb Space Telescope. The photodissociation of this ion is studied here. Accurate explicitly correlated multi-reference configuration interaction {\it ab initio} calculations are done, and full dimensional potential energy surfaces are developed for the three lower electronic states, with a fundamental invariant neural network method. The photodissociation cross section is calculated using a full dimensional quantum wave packet method, in heliocentric Radau coordinates. The wave packet is represented in angular and radial grids allowing to reduce the number of points physically accessible, requiring to push up the spurious states appearing when evaluating the angular kinetic terms, through a projection technique. The photodissociation spectra, when employed in astrochemical models to simulate the conditions of the Orion Bar, results in a lesser destruction of CH$_3^+$ compared to that obtained when utilizing the recommended values in the kinetic database for astrochemistry (KIDA).