Dissociative electron attachment to gas-phase formamide

Abstract

Dissociative electron attachment (DEA) to gaseous formamide, HCONH₂, has been investigated in the energy range between 0 eV and 18 eV using a crossed electron/molecule beam technique. The negative ion fragments have been comprehensively monitored and assigned to molecular structures by comparison with the results for two differently deuterated derivatives, namely 1D-formamide, DCONH₂, and N,N,D-formamide, HCOND₂. The following products were observed: HCONH⁻, CONH₂⁻, HCON⁻, OCN⁻, HCNH⁻, CN⁻, NH₂⁻/O⁻, NH⁻, and H⁻. NH₂⁻ was also separated from O⁻ by using high-resolution negative ion mass spectrometry. Four resonant dissociation channels can be resolved, the strongest ones being located between 2.0 and 2.7 eV and between 6.0 and 7.0 eV. CN⁻ as the most abundant fragment and HCONH⁻ are the dominant products of the first of these two resonances. The most important products of the latter resonance are NH₂⁻, CN⁻, H⁻, CONH₂⁻, and OCN⁻. It is thus found that the loss of neutral H is a site-selective process, dissociation from the N site taking place between 2.0 and 2.7 eV while dissociation from the C site occurs between 6.0 and 7.0 eV. The suitability of these reactions and thus of formamide as an agent for electron-induced surface functionalisation is discussed.