The ZCC model invokes vibrational channel specific "detachment orbitals" and attributes this behavior to coupling of the electronic and nuclear motion in the parent anion. The spatial extent of the model detachment orbital is dependent on the final state of O 2 : the higher the neutral vibrational excitation, the larger the electron binding energy. Although vibronic coupling is ignored in most theoretical treatments of PADs in the direct photodetachment of molecular anions, the present findings clearly show that it can be important. These results represent a benchmark data set for a relatively simple system, upon which to base rigorous tests of more sophisticated models.
Photoelectron imaging probes both molecular electronic structure and electron molecule interactions. In the current work images were recorded for detachment from the I(-) x C(4)H(5)N (I(-) x pyrrole) cluster anion at wavelengths between 360 and 260 nm. The direct detachment spectra show strong similarities to those of I(-), although a strong solvent shift, broadening and some structure is observed. A nondirect, dissociative or autodetachment feature is also observed over a range of wavelengths. Ab initio calculations identify several local minima associated with neutral and anion isomers. Energy and Franck-Condon arguments are used to assess the role of these in the detachment process. The cluster anion structure is essentially an I(-) atomic anion in the presence of a neutral pyrrole molecule. The spectral structure arises due to interactions in the open shell neutral cluster residue resulting from detachment. The indirect detachment feature arises through the formation of an intermediate dipole bound cluster anion state which subsequently dissociates. The energy dependence of this channel (observed over a 0.6 eV range of photon energies) is discussed in terms of the wide amplitude motions associated with the van der Waals modes of the cluster anions.
I(-) x H(2)O and I(-) x CH(3)CN cluster anion photodetachment properties (photoelectron spectra and angular distributions) are recorded via velocity mapped photoelectron imaging for wavelengths between 270 and 340 nm, in small energy increments. These are compared with free I(-) detachment results and reveal the presence of a sharp change in the angular distribution for the (2)P(3/2) spin orbit channel in the vicinity of the (2)P(1/2) threshold. The effect is seen at this threshold in the I(-) x H(2)O cluster anion and just below threshold for I(-) x CH(3)CN. The effect is attributed to an electronic autodetachment process, which is dependent on electronic energy transfer mediated by the electron-neutral complex produced in the excitation process. These results highlight the potential of cluster anion detachment as a probe of electron-molecule interactions and in particular the sensitivity of the angular distributions to intracluster electron transfer processes.
The electron kinetic energy dependence of the photoelectron spectra and angular distributions of I(-)⋅CH(3)X (X=Cl,Br,I) cluster anions are measured via velocity mapped imaging at wavelengths between 350 and 270 nm. Processes analogous to those encountered in free CH(3)X-electron interactions are revealed. In particular, the presence and energies of resonances associated with a low lying σ(∗) state have a marked effect on the results of I(-)⋅CH(3)X photoexcitation. These effects (vibrational excitation, product anion production, and alteration of the photoelectron angular distribution) are far more prominent for I(-)⋅CH(3)I. However, in the vicinity of the (2)P(1/2) threshold there is a sharp deviation in the (2)P(3/2) channel angular distribution and an enhancement of the (2)P(3/2) channel vibrational structure of all three cluster anions. These latter effects are specific to the cluster anion environment through the relaxation of the partner excited I atom and subsequent electronic autodetachment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.