Vibrational Mode Selectivity in Dissociative Ionization of 2-Ethoxyethanol: An IR-VUV NRIFD-IR Spectroscopic Study

In the current work, we studied the infrared spectroscopy of neutral and cationic 2-ethoxyethanol (CH₃CH₂O CH₂CH₂OH, 2-EE) using the infrared (IR)–vacuum-ultraviolet (VUV) non-resonant ionization and fragmentation detected IR spectroscopy (NRIFD-IR) technique. The spectral range was from 2700 cm⁻¹ to 7250 cm⁻¹. Upon radiation with a 118 nm laser, signals corresponding to the cationic 2-EE (m/z=90) and dissociative ionization products (m/z=72, 59, 46, and 45) were detected. The action IR spectra, derived from the signal variations of 2-EE and its fragments upon IR radiation, display differences, suggesting vibrational mode selectivity in the dissociative ionization process. To complement the experimental findings, we performed density functional theory calculations at the B3LYP-D3(BJ)/def2-TZVPP level to determine the structures and anharmonic IR spectra of neutral and cationic 2-EE. The computed spectra showed good agreement with the experimental results.