Collision-Energy-Resolved Penning Ionization Electron Spectroscopy of HCOOH, CH₃COOH, and HCOOCH₃by Collision with He*(2³S) Metastable Atoms

Abstract

Penning ionization of formic acid (HCOOH), acetic acid (CH3COOH), and methyl formate (HCOOCH3) upon collision with metastable He*(2(3)S) atoms was studied by collision-energy/electron-energy-resolved two-dimensional Penning ionization electron spectroscopy (2D-PIES). Anisotropy of interaction between the target molecule and He*(2(3)S) was investigated based on the collision energy dependence of partial ionization cross sections (CEDPICS) obtained from 2D-PIES as well as ab initio molecular orbital calculations for the access of a metastable atom to the target molecule. For the interaction potential calculations, a Li atom was used in place of He*(2(3)S) metastable atom because of its well-known similarity in interaction with targets. The results indicate that in the studied collision energy range the attractive potential localizes around the oxygen atoms and that the potential well at the carbonyl oxygen atom is at least twice as much as that at the hydroxyl oxygen. Moreover we can notice that attractive potential is highly anisotropic. Repulsive interactions can be found around carbon atoms and the methyl group.

An (e,2e) coincidence study of formic acid monomer and dimer

“…Our (e,2e) MO binding energies are in excellent agreement with the previous experimental results [2,3,6]. Our SAOP/pVQZ and OVGF/TZVP calculations also…”

“…2. Table 3 summarises the present orbital assignments and experimental and theoretical binding energies, along with previous results [2,3,6], for the formic acid monomer.…”

“…The valence electronic structures of formic acid monomer and dimer have been studied extensively by photoelectron spectroscopy (PES) [2][3][4][5] but electron collision studies are limited. A previous EMS study by Bharathi et al [6] was conducted at room temperature where formic acid vapour contains considerable dimer concentration [7].…”

“…This was done using a least squares minimization procedure [30] employing a Gaussian function for each MO. Each MO width was set to a value representing the convolution between the instrument resolution and the MO width observed in high resolution PES studies[2][3][4][5]. The dominant contribution is generally from the coincidence energy resolution.Monomer and dimer binding energies were allowed to vary from the PES values to improve the agreement between the measured BES and synthesized spectra.…”

Photodissociation of methyl formate in circumstellar environment: stability under soft X-rays

“…Following this line, Jackson et al (2005) have investigated the molecular fragments released from the collision of methyl formate with energetic ions, such as N + 2 , NH + 2 and NH + 3 , in an attempt to produce glycine precursors. The collision of HCOOCH 3 with He atoms has also been investigated by Borodin et al (2005) in an attempt to understand its interaction potential chemical processes and reactions.…”