Energy effects in collisional neutralization with organic molecules

Area of Science:

• Physical Chemistry
• Mass Spectrometry
• Chemical Physics

Background:

• Understanding ion-molecule reactions is crucial for various chemical processes.
• Neutralization-reionization mass spectrometry (NRMS) probes ion internal energies.
• Franck-Condon effects play a key role in electron transfer processes.

Purpose of the Study:

• To investigate the neutralization-reionization of methanol (CH3OH+.), methylamine (CH3NH2+.), and dimethylamine ((CH3)2NH+.) ions.
• To determine the internal energy distributions of reionized ions under varying electron transfer conditions (exothermic and endothermic).
• To analyze the influence of precursor ion internal energy on survivor ion abundances.

Main Methods:

• Utilized neutralization-reionization mass spectrometry at kiloelectronvolt collision energies.
• Employed Gaussian-2 level calculations to determine vertical recombination and ionization energies.
• Analyzed Franck-Condon effects on vibrational modes affected by vertical electron transfer.

Main Results:

• Internal energy deposition during neutralization is primarily governed by Franck-Condon effects.
• Electron transfer energy balance has minimal impact on the high-energy fraction of reionized molecules.
• Precursor ion internal energy significantly affects the relative abundances of survivor ions.

Conclusions:

• Franck-Condon effects dictate energy deposition in neutralization-reionization of small organic ions.
• Electron transfer from low-lying molecular orbitals occurs during random ion-molecule orientations.
• Calculated recombination energies differ notably from ionization energies, highlighting Franck-Condon impacts.