Observation of Renner-Teller and predissociation coupled vibronic intensity borrowing in dissociative electron attachment to OCS.

We use a time-of-flight-based velocity map imaging method to look into the dissociative electron attachment to a linear OCS molecule at electron beam energies ranging from 4.5 to 8.5 eV.

Dissociative electron attachment to carbon tetrachloride probed by velocity map imaging.

Bond-breaking in CCl dissociative electron attachment (DEA) has been studied using a velocity map imaging (VMI) spectrometer. A number of effects related to the dissociation dynamics have been revealed. The near-zero eV -wave electron attachment, which leads to the production of Cl anions, is accompanied by a very efficient intramolecular vibrational redistribution.

Fragmentation dynamics and absolute dissociative electron attachment cross sections in the low energy electron collision with ethanol.

Dissociative electron attachment (DEA) to ethanol has been probed to study fragmentation dynamics using Time-of-Flight (ToF) mass spectrometric technique. Several fragment ions, namely, H, O, OH, CHO and CHO have been observed. Extra effort has been made to detect low mass ions (here, H).

Breakdown of dipole Born approximation and the role of Rydberg's predissociation for the electron-induced ion-pair dissociation to oxygen in the presence of background gases.

We study the electron-induced ion-pair dissociation to gas-phase oxygen molecules using a state-of-the-art velocity-map ion-imaging technique. The analysis is entirely based on the conical time-gated wedge-shaped velocity slice images of O-/O2 nascent anionic fragments, and the resulting observations are in favor of Van Brunt et al.'s report [R.

Dissociative electron attachment dynamics of carbon disulfide and violation of axial recoil approximation near 6 eV resonance.

Complete dissociation dynamics of low-energy electron attachment to carbon disulfide have been studied using the velocity slice imaging (VSI) technique. The ion yields of the different fragment anions produced due to the dissociative electron attachment to carbon disulfide for the 5 to 11 eV incident electron energy range have been collected. Two resonances for S ions are observed at around 6.

Dissociation dynamics in low energy electron attachment to ammonia using velocity slice imaging.

The complete dissociation dynamics of low energy electron attachment to the ammonia molecule has been studied using velocity slice imaging (VSI) spectrometry. One low energy resonant peak around 5.5 eV and a broad resonance around 10.

A new time of flight mass spectrometer for absolute dissociative electron attachment cross-section measurements in gas phase.

A new time of flight mass spectrometer (TOFMS) has been developed to study the absolute dissociative electron attachment (DEA) cross section using a relative flow technique of a wide variety of molecules in gas phase, ranging from simple diatomic to complex biomolecules. Unlike the Wiley-McLaren type TOFMS, here the total ion collection condition has been achieved without compromising the mass resolution by introducing a field free drift region after the lensing arrangement. The field free interaction region is provided for low energy electron molecule collision studies.

Dipolar dissociation dynamics in electron collisions with carbon monoxide.

Dipolar dissociation processes in the electron collisions with carbon monoxide have been studied using time of flight (TOF) mass spectroscopy in combination with the highly differential velocity slice imaging (VSI) technique. By probing ion-pair states, both positive and/or negative ions may be detected. The ion yield curve of negative ions provides the threshold energy for the ion-pair production.

Fragmentation dynamics in dissociative electron attachment to CO probed by velocity slice imaging.

Complete dissociation dynamics in electron attachment to carbon monoxide (CO) have been studied using the newly developed velocity slice imaging (VSI) technique. Both kinetic energy and angular distributions of O(-) ions formed by dissociative electron attachment (DEA) to CO molecules have been measured for 9, 9.5, 10, 10.

Dissociative electron attachment to N2O using velocity slice imaging.

The structure and dynamics of the negative ion resonances leading to dissociative electron attachment in N2O are studied using the velocity slice imaging technique. Distinct momentum distributions are observed in the O(-) channel for the dominant resonances below 4 eV which are considerably different than those reported so far. Also the relatively weak but distinct resonances at 8.

A roaming wavepacket in the dynamics of electronically excited 2-hydroxypyridine.

How much time does it take for a wavepacket to roam on a multidimensional potential energy surface? This combined theoretical and pump-probe femtosecond time experiment on 2-hydroxypyridine proposes an answer. Bypassing the well-established transition state and conical intersection relaxation pathways, this molecular system undergoes relaxation into the S1 excited state: the central ring is destabilized by the electronic excitation, within ~100 fs after absorption of the pump photon, then the H-atom bound to oxygen undergoes a roaming behavior when it couples to other degrees of freedom of the molecule. The timescale of the latter process is measured to be ~1.

Atomic selectivity in dissociative electron attachment to dihalobenzenes.

We investigated electron attachment to three dihalobenzene molecules, bromochlorobenzene (BCB), bromoiodobenzene (BIB) and chloroiodobenzene (CIB), by molecular beam photoelectron spectroscopy. The most prominent product of electron attachment in the anion mass spectra was the atomic fragment of the less electronegative halogen of the two, i.e.

Dissociative electron attachment to NO probed by velocity map imaging.

An experimental and theoretical investigation of the dissociative electron attachment process in nitric oxide is presented. Measurements using the recently developed ion momentum imaging conclusively show the presence of two resonance features in the O(-) channel. These are found to dissociate to give N atoms in the (2)D and (2)P excited states respectively, thus settling the controversies regarding the possible dissociation limits of this process.

Excitation mechanism in the photoisomerization of a surface-bound azobenzene derivative: Role of the metallic substrate.

Two-photon photoemission spectroscopy is employed to elucidate the electronic structure and the excitation mechanism in the photoinduced isomerization of the molecular switch tetra-tert-butyl-azobenzene (TBA) adsorbed on Au(111). Our results demonstrate that the optical excitation and the mechanism of molecular switching at a metal surface is completely different compared to the corresponding process for the free molecule. In contrast to direct (intramolecular) excitation operative in the isomerization in the liquid phase, the conformational change in the surface-bound TBA is driven by a substrate-mediated charge transfer process.

Functional group dependent dissociative electron attachment to simple organic molecules.

Dissociative electron attachment (DEA) cross sections for simple organic molecules, namely, acetic acid, propanoic acid, methanol, ethanol, and n-propyl amine are measured in a crossed beam experiment. We find that the H(-) ion formation is the dominant channel of DEA for these molecules and takes place at relatively higher energies (>4 eV) through the core excited resonances. Comparison of the cross sections of the H(-) channel from these molecules with those from NH(3), H(2)O, and CH(4) shows the presence of functional group dependence in the DEA process.

Functional group dependent site specific fragmentation of molecules by low energy electrons.

Functional group dependence is observed in the dissociative electron attachment (DEA) to various organic molecules in which the DEA features seen in the precursor molecules of the groups are retained in the bigger molecules. This functional group dependence is seen to lead to site-selective fragmentation of these molecules at the hydrogen sites. The results are explained in terms of the formation of core-excited Feshbach resonances.