CH(+) Destruction by Reaction with H: Computing Quantum Rates To Model Different Molecular Regions in the...

Area of Science:

• Astrochemistry
• Interstellar Medium Chemistry
• Quantum Chemistry

Background:

• The carbon chemistry of the interstellar medium (ISM) is crucial for understanding molecular formation.
• CH(+) is a key ion in ISM carbon chemistry, but its abundance is not fully understood.
• Existing experimental and theoretical data on CH(+) destruction rates show discrepancies.

Purpose of the Study:

• To compute accurate ab initio reactive cross sections for a key ionic reaction in ISM carbon chemistry.
• To determine CH(+) destruction rates across a range of temperatures.
• To model the impact of these rates on CH(+) abundance in various ISM environments.

Main Methods:

• Quantum mechanical calculations to compute ab initio reactive cross sections.
• Numerical modeling to obtain CH(+) destruction rates.
• Incorporation of new rates into a complex chemical network using the krome package.
• Solving coupled, first-order kinetics equations to model CH(+) abundance evolution.

Main Results:

• Computed CH(+) destruction rates show good agreement with existing experiments.
• Differences between calculations and low-temperature experiments are linked to collinear approaches and nonadiabatic crossing.
• CH(+) destruction is significant at temperatures above 100 K in astrochemical environments.
• A slight decrease in initial oxygen abundance may lead to higher CH(+) abundances.

Conclusions:

• Low-temperature experimental discrepancies have minimal impact on CH(+) abundance in typical ISM conditions.
• Other chemical processes dominate CH(+) destruction at lower temperatures relevant to ISM.
• A revised understanding of CH(+) destruction and formation pathways may resolve discrepancies in astrochemical models.