Dissociative photodetachment vs. photodissociation of aromatic carboxylates: the benzoate and naphthoate anions

Abstract

Photodetachment leads to a stable radical and to dissociation. Both processes are characterized by the kinetic energy release of the neutral particles.

Photofragmentation and electron detachment of aromatic phosphonate, sulfonate and phosphate oxyanions

“…The experimental setup used to measure cold ion photofragmentation (PF) and photodetachment (PD) spectra was described in previous publications [24][25][26] . The apparatus was recently modified to detect negative ions and the neutral particles originating from both the electron detachment process and following fragmentation 1,2 . The oxyanions are produced in an electrospray ionisation (ESI) source by deprotonation of phenylphosphonic, phenylphosphoric, phenylsulfonic, and p-toluenesulfonic acids.…”

“…When operating in neutral detection mode, the ions are deflected away from the detector, and only the yield of neutral particles is quantified. By applying this method, the PD process becomes experimentally accessible and the ADE can be determined by observing the onset of the narrow central peak corresponding to the arrival of neutral radicals at the detector (see the examples in the SI and in our recent publications 1,2 ).…”

“…The photophysical properties of isolated aromatic carboxylates (Ar-CO2  , with Ar representing the aryl residue) have recently been explored in the UV region of the spectrum. 1,2 In such systems, photoexcitation has been shown to lead to a competition between electron detachment followed by decarboxylation, and dissociative ionic channels producing neutral and anionic fragments. However, there is no information available in the literature about the gas phase spectroscopic behaviour of analogous oxyanions containing phosphorus or sulfur atoms such as, for example, aryl phosphonates (Ar-PO3H  ) and sulfonates (Ar-SO3  ).…”

“…As the photon energy increases, electron photodetachment becomes ever faster and it soon becomes the dominant process. Moreover, once the electron is detached from the anion, the resulting neutral radical species may potentially dissociate giving rise to two neutral fragments 1 . In addition to valence excited states and autodetaching resonances, molecular anions can be excited to dipole bound states (DBS), which resemble the Rydberg states in neutral molecules.…”

Photodetachment of deprotonated aromatic amino acids: stability of the dehydrogenated radical depends on the deprotonation site

“…Photodissociation in the ion trapNone of the deprotonated aromatic amino acids led to the production of any ionic fragment when the interaction with the laser took place in the ion trap, indicating that there are no optically accessible excited states below the photodetachment threshold, in contrast with the case of naphthoate(Pino et al 2019). b) Photodetachment in the Gauss tube [Phe-H]anionAs presented in the experimental section, intact radicals appear as narrow peaks while fragments appear as broadened peaks.…”