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

Self Cite

An approximate model for analytical prediction of photoelectron angular distributions in anion photodetachment from mixed s-p states is presented. Considering the dipole-allowed s, p, and d free-electron partial waves, the model describes photodetachment anisotropy in terms of the fractional p character of the initial orbital and the A and B coefficients describing the relative intensities of the p → d to p → s and s → p to p → s channels, respectively. The model represents an extension of the central-potential model to an intermediate regime encompassing varying degrees of s and p contributions to the initial bound orbital. This description is applicable to a broad class of hybrid molecular orbitals, particularly those localized predominantly on a single atom. Under the additional assumption of hydrogenic or Slater-type orbitals, the B/A ratio in photodetachment from a mixed 2s-2p state is shown to equal 8/3. Corresponding fractions are derived for other ns-np mixing cases. The predictions of the model are tested on several anion systems, including NH(2)(-) and CCl(2)(-). The quantitative discrepancies in the latter case are attributed to the breakdown of the central-atom approximation and a mechanism for corresponding corrections is indicated.

Section: Introductionmentioning

confidence: 99%

Photodetachment anisotropy for mixed s-p states: 8/3 and other fractions

Sanov

Grumbling

Goebbert

et al. 2013

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“…51 It is noted that peaks g and i are much broader than peaks e, f , and h, indicating that several close-lying transitions may contribute to these two peaks. The PAD can be difficult to interpret for complex molecules, 47 but still can provide valuable electronic information. The PADs show that features 0 0 0 , b-d all have s-wave character while peaks e-i all have p-wave character (Fig.…”

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confidence: 99%

“…[42][43][44][45] One advantage of PE imaging is the PAD, which provides information about the nature of the occupied molecular orbital from which the electron is ejected. 46,47 The acetate anions were generated by electrospray of 1 mM solution of CH 3 COONa dissolved in a mixed CH 3 OH/H 2 O solvent (9:1 volume ratio). After passing through two radio-frequency (RF) quadrupole ion guides and one RF-only octopole ion guide, the anions were loaded into a cryogenically cooled Paul trap in a more compact linear configuration, 13 compared with our first generation cold ion trap.…”

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confidence: 99%

Communication: Observation of dipole-bound state and high-resolution photoelectron imaging of cold acetate anions

Huang

Zhu

Wang

2015

We report the observation of a dipole-bound state and a high-resolution photoelectron imaging study of cryogenically cooled acetate anions (CH3COO−). Both high-resolution non-resonant and resonant photoelectron spectra via the dipole-bound state of CH3COO− are obtained. The binding energy of the dipole-bound state relative to the detachment threshold is determined to be 53 ± 8 cm−1. The electron affinity of the CH3COO neutral radical is measured accurately as 26 236 ± 8 cm−1 (3.2528 ± 0.0010 eV) using high-resolution photoelectron imaging. This accurate electron affinity is validated by observation of autodetachment from two vibrational levels of the dipole-bound state of CH3COO−. Excitation spectra to the dipole-bound states yield rotational profiles, allowing the rotational temperature of the trapped CH3COO− anions to be evaluated.

“…(4). 1,18 Equation (4) has a form that is superficially similar to Eq. (2), and it reduces to the same expression given by Eq.…”

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confidence: 99%

“…In an effort to retain the similar insight offered by the atomic treatment, a model has been developed for photodetachment from a mixed sp type molecular orbital. 1,18 This model applies to a system where electrons are detached from a molecular orbital that can be approximated as a linear combination of one s and one p type functions at the same atomic center:…”

mentioning

confidence: 99%

Communication: Photoelectron angular distributions of CH− reveal a temporary anion state

Bandyopadhyay

Pruitt

Goebbert

2013

Photoelectron imaging has broadened the scope of traditional photoelectron spectroscopy by combining a simultaneous photoelectron angular distribution, PAD, measurement with kinetic energy analysis. A fundamental understanding of PADs has been largely limited to simple atomic systems. However, a new model has recently been developed that predicts PADs as a function of electron kinetic energy for a simple linear combination of s and p atomic orbitals. We used CH− to test this model by acquiring PADs in a photoelectron imaging spectrometer at wavelengths from 600 to 355 nm. The PADs for electron detachment from the HOMO (1π) of CH− fit model predictions. However, the PADs associated with detachment from the HOMO-1 (3σ) orbital exhibit anomalous behavior at low electron kinetic energies because of a resonant process that arises from a previously undetected excited state of CH−.