The effect of intracluster photoelectron interactions on the angular distribution in I−⋅CH3I photodetachment

Abstract

I(-) and I(-)*CH(3)I velocity mapped photodetachment images are recorded over wavelengths between 270 and 370 nm. Spectral similarities, in conjunction with ab initio calculations show that the cluster anion comprises an atomic iodide anion moiety solvated by a relatively unperturbed CH(3)I molecule. Between 340-370 nm and at 280 nm, free I(-) is produced via a process analogous to dissociative electron attachment within the cluster anion. More strikingly, the photoelectron angular distribution for each species at a given electron kinetic energy is very different, despite detachment occurring from the iodide 5p orbital in each case. These observations reveal the effect of interaction of the photoelectron with the neutral cluster residue and are discussed in terms of resonances associated primarily with the CH(3)I molecule.

Inter-channel effects in monosolvated atomic iodide cluster anion detachment: Correlation of the anisotropy parameter with solvent dipole moment

“…The photoelectron velocity mapped imaging spectrometer used in this study has been described in detail before 3 and only a brief description is given below. Anions are generated by supersonic expansion of an appropriate gas mixture through a pulsed nozzle (General Valve, Series 9) and pulsed DC (−900 -−500 V, 15 μs pulses) discharge assembly.…”

“…[4][5][6] To date, only I − · CH 3 Br and I − · CH 3 I PADs have been observed to show a strong deviation from those of I − detachment at photon energies more than 100 meV below the channel II threshold. [2][3][4]9 These deviations are largely attributable to the effect of a low-lying anionic σ * state associated with the methyl halide molecule rather than the long range electrondipole interaction. 27,28 On the other hand, for excitation in the vicinity of the channel II threshold there is a striking variation from free I − detachment for all cluster anions of the type I − · X.…”

“…[1][2][3][4][5][6] Subject to minor perturbation from the molecular moiety, the highest lying occupied orbitals are essentially those of free I − . 2,3,5,[7][8][9][10] The cluster anion detachment spectra are similar to those of free I − and the transitions observed are most conveniently discussed according to the asymptotic atomic iodine states produced. Subsequently, we will use the labels channel I and channel II to refer to transitions correlating to the production of [I( 2 P 3/2 ) + X + e − ] and [I( 2 P 1/2 ) + X + e − ], respectively.…”

Photoelectron angular distributions in negative-ion photodetachment from mixed sp states

“…[21][22][23][24] However, decades of successful and diverse applications of Hanstorp et al's approach 20 appear to suggest that, while the Wigner law predictions of partial wave cross sections are not accurate outside the threshold regime, its predictions of cross section ratios probably are. 10,18,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Assuming σ i +1 /σ i −1 ∝ ε 2 and, therefore,…”

Solvation effects on angular distributions in H−(NH3)n and NH2−(NH3)n photodetachment: Role of solute electronic structure

“…[23][24][25] The third (post-detachment) motif, manifest in the presence of electron-solvent scattering resonances, was also discussed in several recent publications. [23][24][25][26][27] In this work, we address the effect of solvation-induced changes in the parent orbital symmetry (i.e., the second of the above motifs) by examining PADs for two solvation series, with the same solvent but different solutes with distinct parent orbitals.…”