The assignment of dissociative electron attachment bands in compounds containing hydroxyl and amino groups

Abstract

Abstract. Dissociative electron attachment (DEA) spectra were recorded for methanol, phenol, diethylamine, tetramethylhydrazine, piperazine, pyrrole and N,Ndimethylaniline. Comparison with HeI photoelectron spectra permitted the assignment of virtually all DEA bands in the saturated compounds to core excited Feshbach resonances with double occupation of Rydberg-like orbitals and various Koopmans' states of the positive ion as a core. These resonances shift to lower energies with alkyl substitution, in contrast to the shape resonances, and are found at surprisingly low energies in the amines. The DEA spectra in the unsaturated compounds show no or only weak evidence for the Rydberg-type Feshbach resonances. It is proposed that DEA in saturated polyatomic molecules containing hydroxyl and amino groups is in general dominated by this type of resonances.

Computation of electron-impact rotationally elastic total cross sections for methanol over an extensive range of impact energy (0.1 – 2000 eV)

“…In the present calculation, the 2A state shows a prominent structure at 8.5 eV, which is in agreement with the earlier predicted values of 8.81 eV [3], 7.9 eV [48], and 8.0 eV [49]. Similarly, another structure is seen in the 2A state at 10.57 eV, which is in agreement with earlier reported values of 11.71 eV [3], 10.5 eV [48], and 10.2 eV [49], which can be visualized as a peak around 11 eV in the TCS curve. It is to be noted that as more states are included in the close-coupling (CC) expansion and retained in the outer region calculation, the eigenphase sum increases, reflecting the improved modeling of the polarization interaction.…”

“…The electronic excitations to 3A and 1A show sharp increases near their respective thresholds which show the dominance of these energy levels in the present calculation. The notable structure in 3A around 11 eV is reflected as a broad peak around 11 eV in TCSs and is in accordance with the experimental prediction of Skalicky and Allan [48] at 11.82 eV. Beyond 12 eV no prominent structures are observed.…”

“…A resonance with 2A symmetries was located at 6.4 eV by Skalicky and Allan [48], at 6.5 eV by Prabhudesai et al [49], and calculated by Bouchiha et al [3] to lie at 6.75 eV. A second resonance with 2A symmetries was identified at 7.9 eV by Skalicky and Allan [48], 8 eV by Prabhudesai et al [49], and calculated by Bouchiha et al [3] to be at 8.81 eV, and a third resonance with 2A symmetry was found around 10.5 eV by Skalicky and Allan [48], 10.2 eV by Prabhudesai et al [49], and calculated by Bouchiha et al [3] to be at 11.73 eV [3]. Figure 1 shows the eigenphase diagram for two doublet scattering states (2A and 2A ) of the CH 3 OH system using HF and CI models.…”

A dramatic difference between the electron-driven dissociation of alcohols and ethers and its relation to Rydberg states

“…2. These resonances, belonging to deeper ionizations, were discussed in more detail earlier 3,4 and are not of primary concern in this work.…”

Electron-induced chemistry of alcohols

“…[5][6][7][8][9][10] In our earlier work we studied several saturated compounds containing the amino-and the hydroxyl groups which could be considered as model compounds for biomolecules. 11 We used the comparison between the HeI photoelectron spectra and the DEA spectra to identify the Feshbach resonances and to assign the DEA bands and found that all DEA bands could be explained by Feshbach resonances, the low-lying ones being localized on the functional groups. In the present paper we substantially extend the work on the alcohols and report several new findings, in particular, the involvement of shape resonances at low energies, dramatic isotope effects, cases of state and site selective chemistry, and more insight into the mechanism of fragmentation of Feshbach resonances.…”