A photodetachment imaging study of the photoelectron angular distributions produced by the 354.8-nm photodetachment of the vinoxide anion, H2CCHO-, is reported. The photoelectron angular distributions for both the X̃ 2 A ‘ ‘ ground state and à 2 A ‘ excited state of the neutral vinoxy radicals were measured. Energy-dependent photoelectron anisotropy parameters are reported for both electronic states. Photodetachment from the HOMO of the anion (the CCO nonbonding π(a‘ ‘) orbital) yields ground-state vinoxy radicals and exhibits a sin2 θ angular dependence (β (X̃ 2 A ‘ ‘) = −0.7 ± 0.1) relative to the electric vector of the laser. Photodetachment from the HOMO-1 of the anion (the oxygen σ2px(a‘) orbital) yields excited-state à 2 A‘ radicals and exhibits a cos2 θ angular dependence (β (à 2 A ‘) = 0.6 ± 0.1) of the photoelectrons. These results are qualitatively interpreted in terms of the electronic structure of the anion−neutral system.

The SPEAR (or 'FIMS') instrumentation has been used to conduct the first large-scale spectral mapping of diffuse cosmic far ultraviolet (FUV, 900-1750 AA) emission, including important diagnostics of interstellar hot (10^4 K - 10^6 K) and photoionized plasmas, H_2, and dust scattered starlight. The instrumentation's performance has allowed for the unprecedented detection of astrophysical diffuse far UV emission lines. A spectral resolution of 550 and an imaging resolution of 5' is achieved on-orbit in the Short (900 - 1175 AA) and Long (1335 - 1750 AA) bandpass channels within their respective 7.4 deg x 4.3' and 4.0 deg x 4.6' fields of view. We describe the SPEAR imaging spectrographs, their performance, and the nature and handling of their data

Photoelectron-photofragment coincidence spectroscopy of I- (CO2), I- (NH3), I- (H2O), I- (C6H5NH2), and I- (C6H5OH) clusters was used to study the dissociative photodetachment (DPD) dynamics at 257 nm. Photodetachment from all five clusters was observed to yield bound neutral clusters as well as the DPD products of the iodine atom and the molecular solvent. Photoelectron images and kinetic energy spectra were recorded in coincidence with both the translational energy released between dissociating neutral products and stable neutral clusters. The variation of the photoelectron angular distributions in the clusters was measured, revealing significant perturbations relative to I- for I- (H2O) and I- (C6H5NH2). Product branching ratios for stable versus dissociative photodetachment and photodetachment to the I(2P(3/2)) and I(2P(1/2)) states are reported. The measurements reveal a dependence of the DPD dynamics on the final spin-orbit state of iodine in the cases of I- (C6H5NH2) and I- (CO2) and a threshold detachment process in I- (C6H5NH2).

The "Spectroscopy of Plasma Evolution from Astrophysical Radiation" (SPEAR, also known as the "FarUltraviolet Imaging Spectrograph") instruments, flown aboard the STSAT-1 satellite mission, have provided the first large-area spectral mapping of the cosmic far-ultraviolet (FUV; 900-1750 ) background. We describe the A mission and its science motivation, the mission data and their processing, and the effects of mission performance on the science data. We present the first map of the cosmic FUV background (1360-1710 ) over most of the A sky as an example of the mission results. These SPEAR data reveal diffuse radiation from warm and hot (10 4 -10 6 K) plasma, molecular hydrogen fluorescence, and dust-scattered starlight. They allow for an unprecedented characterization of the spectral emission from a variety of environments, including the general interstellar medium (ISM), molecular clouds, supernova remnants, and superbubbles.

This methodology permits a sensitive, quantitative, clinically useful representation of the pre-cataractous molecular changes associated with aging in the living human lens.