Regular Article

On the electronic structure of methyl butyrate and methyl valerate^★,★★

¹ Department of Control and Power Engineering, Faculty of Ocean Engineering and Ship Technology, Gdańsk University of Technology, Gabriela Narutowicza 11/12, Gdańsk 80-233, Poland
² Univ. Lille, CNRS, UMR 8523 – PhLAM – Physique des Lasers Atomes et Molcules, Lille 59000, France
³ ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade, Building 1520, Aarhus C 8000, Denmark
⁴ Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon S7N 2V3, Canada
⁵ School of Physical Sciences, Ingram Building, University of Kent, Canterbury CT2 7NH, UK
⁶ Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, Caparica 2829-516, Portugal

^a e-mail: smialek@pg.edu.pl

Received: 29 February 2020
Received in final form: 14 April 2020
Published online: 7 July 2020

Abstract

We present novel results of the analysis of the electronic structure of two aliphatic esters: methyl butyrate and methyl valerate. High-resolution photoabsorption spectra were collected and analyzed over the energy range 4.0–10.8 eV and showed for both the molecules not only a clear band of the HOMO to LUMO transition, but also vibronic structure associated with the first Rydberg-valence transition. Photoelectron spectra recorded from 9 to over 28 eV revealed many ionization states with the first adiabatic ionization energies found to be 9.977 eV and 9.959 eV for methyl butyrate and methyl valerate, respectively. Ab initio calculations have been performed in order to help assign the photoabsorption and photoelectron features. Photolysis life times in the atmosphere were calculated revealing that photolysis is not competitive over hydroxyl radical scavenging in the process of removal of these esters from the atmosphere.