Communication: Protonation process of formic acid from the ionization and fragmentation of dimers induced by synchrotron radiation in the valence region

Abstract

Competitive fragmentation pathways of acetic acid dimer explored by synchrotron VUV photoionization mass spectrometry and electronic structure calculations

Ionization and Fragmentation of DCOOD Induced by Synchrotron Radiation at the Oxygen 1s Edge: The Role of Dimer Formation

“…According to them, these ions are evidence of the H (D) transfer reaction in the formic acid, with H 3 O + and HD 2 O + being formed via H 2 O + (HDO + ) precursors of a migration of H (D) in the formic acid molecule. We emphasize that in the previous studies of HCOOH and DCOOD molecules in the valence region, , we also verify the existence of the cations H 2 O + and D 2 O + , whose rise was also due to migration (recombination) of H or D in molecular fragmentation of formic acid.…”

“…Concerning the ion with m/q = 30, the increase in the relative yield with the pressure is even more pronounced for energies above the second resonance. Specifically, we have shown in ref that the appearance of the deuteronated formic acid ((DCOOD)·D + ) and the increase of DCO + yield are a direct consequence of the formation of formic acid dimers due to increased pressure.…”

“…This beamline has a monochromator with spherical diffraction gratings, which selects photons with energies between 250 and 1000 eV and energy resolution of E /Δ E = 1000, for 100 μm slits. The spectrometer allows to collect the PEPICO and PEPIPICO techniques. , The PEPICO and PEPIPICO spectroscopy has been widely used in recent studies − ,− to determine the fragmentation pathways of different molecular species that are single and doubly ionized.…”

“…In previous studies of the photofragmentation of formic acid and formamide in the valence region, we observed the production of a protonated ion, with a mass-to-charge ratio one unit larger than the parent ion. In a recent work we investigated the protonation process of double deuterated formic acid (DCOOD) as a result of dimers photofragmentation in the valence region . The results of that study indicate that deuteronated ions, (DCOOD)·D + , are originated from dimer fragmentation, and we could ascertain the experimental appearance energy of the ion (DCOOD)·D + from the ionization of (DCOOD) 2 .…”

“…The reason we measure the doubly deuterated formic acid is that deuterium is not abundant in nature. Thus, the existence of the deuteronated ion cannot be explained as due to H + capture during the injection of the sample in the experimental chamber or due to the presence of the isotope 13 C (see ref for a detailed discussion). An effusive molecular beam of doubly deuterated formic acid molecules was bombarded by photons with energy in the soft X-ray band, specifically, from 530.0 to 580.0 eV, so that oxygen 1s orbital electrons are excited to more energetic orbitals or to the continuum, causing ionization or dissociative ionization of the molecule.…”