Electron collisions with ammonia and formamide in the low- and intermediate-energy ranges

Abstract

We report an investigation on electron collisions with two nitrogen-containing compounds, namely ammonia (NH 3 ) and formamide (NH 2 CHO). For ammonia, both theoretical and experimental differential, integral, and momentum-transfer cross sections, as well as calculated grand-total and total absorption cross sections, are reported in the 50-500 eV incident energy range. Calculated results of various cross sections are also reported for energies below 50 eV. Experimentally, angular distributions of the scattered electrons were measured using a crossed electron beam-molecular beam geometry and then converted to absolute differential cross sections using the relative flow technique. Absolute integral and momentum-transfer cross sections for elastic e − -ammonia scattering were also derived from the measured differential cross sections. For formamide, only theoretical cross sections are presented in the 1-500 eV incident energy range. A single-center-expansion technique combined with the method of Padé was used in our calculations. For both targets, our calculated cross sections are compared with the present measured data and with the theoretical and experimental data available in the literature and show generally good agreement. Moreover, for formamide, two shape resonances located at 3.5 eV and 15 eV which correspond to the continuum 2 A and 2 A scattering symmetries, respectively, are identified. The former can be associated to the 2 B 1 shape resonance in formaldehyde located at around 2.5 eV, whereas the latter can be related to the 2 E resonance in ammonia at about 10 eV. Such correspondence is very interesting and so supports the investigation on electron interaction with small building blocks, instead of with larger biomolecules.

Theoretical and experimental investigation of electron collisions with acetone

“…As for acetaldehyde, TCS reported by Szmytkowski [13] for acetone also did not present evidence of the π * shape resonance at low incident energies. One possible reason is that both acetaldehyde and acetone are strongly polar targets; therefore the π * shape resonance feature might be masked by the intense dipole-scattering background, as seen in our previous work on formamide [7]. In order to clarify this fact, the present paper reports a theoretical investigation on e − -acetone scattering.…”

“…From a theoretical point of view, electron-assisted processes involving the organic molecules with the carbonyl group in their structures may support a shape resonance due to the existence of an empty π * orbital that may trap electrons to form metastable states. Such resonances were in fact identified in the theoretical studies of low-energy electron collisions with formaldehyde [1][2][3], formic acid [4,5], and, more recently, acetaldehyde [6] and formamide [7]. Experimentally, such resonances were seen in studies involving electron interaction with carbonyl-containing compounds.…”

“…In our calculation, the dynamics of the projectile-target interaction is represented by a molecular complex optical potential (MCOP) at the static-exchangepolarization plus absorption (SEPA) level of approximation. This model has already been applied by our group to study electron collisions with other carbonyl-containing molecules, e.g., formaldehyde [3] and formamide [7]. Also, due to the lack of experimental DCS for this target, we performed measurements of this physical quantity in the 30-800 eV range using the relative-flow technique (RFT).…”

Electron ionization of clusters containing the formamide molecule

“…For example, elastic electron scattering from FA was studied in Refs. [16][17][18][19][20][21] and inelastic electron scattering in [22]. Wang and Tian reported computational results for inelastic electron scattering as well [20].…”

Investigating resonant low-energy electron attachment to formamide: dynamics of model peptide bond dissociation and other fragmentation channels

“…Electron scattering from formamide has been extensively studied previously over a broad range of energies [20][21][22][23]. Studies of the dissociation pathways of formamide irradiated by (vacuum) ultraviolet light [24,25] or higher energy radiation [26][27][28] have revealed chemical products of biological and technological relevance.…”