A recoil ion momentum spectrometer for molecular and atomic fragmentation studies

Abstract

We report the development and performance studies of a newly built recoil ion momentum spectrometer for the study of atomic and molecular fragmentation dynamics in gas phase upon the impact of charged particles and photons. The present design is a two-stage Wiley-McLaren type spectrometer which satisfies both time and velocity focusing conditions and is capable of measuring singly charged ionic fragments up-to 13 eV in all directions. An electrostatic lens has been introduced in order to achieve velocity imaging. Effects of the lens on time-of-flight as well as on the position have been investigated in detail, both, by simulation and in experiment. We have used 120 keV proton beam on molecular nitrogen gas target. Complete momentum distributions and kinetic energy release distributions have been derived from the measured position and time-of-flight spectra. Along with this, the kinetic energy release spectra of fragmentation of doubly ionized nitrogen molecule upon various projectile impacts are presented.

Fragmentation dynamics of doubly charged camphor molecule following C 1s Auger decay

“…Ion hits on the delay-line detector in the VMI spectrometer were referenced to the arrival time of the electron at the detector in the ToF spectrometer, and arrival time differences were used to determine the three momentum components. These components were computed as follows: 55,56…”

Velocity and charge-state dependence on the Coulomb explosion of N2, under the impact of highly-charged ions at intermediate velocities

“…In contrast, the contribution from the high-lying states goes on decreasing as the energy deposited to the system decreases. This explains the systematic depletion of the contribution coming from region C which arises from the highlying excited states of N 2 2+ [10,35,41]. It is worth mentioning that in the present experiment, we are not sensitive to the pure double (or triple for N 2 3+ ) electron-capture processes as we get the start signal from the electrons (see the experimental section).…”

“…The experiment is performed at the electron cyclotron resonance-based ion accelerator (ECRIA) of Tata Institute of Fundamental Research, Mumbai [33,34]. Details of the experimental apparatus and the data acquisition system used in this experiment have been described elsewhere [35]. Therefore, here we will give a concise description of the experimental setup.…”

“…] with vertical energies of 67.4 eV and 70.8 eV, respectively) [7,10,35,40,41]. The differences in the vertical energy required for different electronic states assert that the population of the higher KER peaks needs a higher amount of energy deposition to the neutral N 2 molecule.…”

Unravelling the molecular phenomena of hydrogen peroxide (H2O2) through many-body fragmentation dynamics

“…This Ar 8+ and effusive jet of H2O2 molecules were crossed at right angles at the center of the pusher and puller electrodes of the recoil-ion momentum spectrometer (RIMS). The fullest details of the RIMS were detailed elsewhere [34]. The electrons ejected after the interaction between Ar 8+ and H2O2 were extracted in the opposite direction and collected by channel-electron multiplier (CEM), will serve as the 'START' of the coincidence measurement whereas the fragmented ions do serve as the 'STOP' signal.…”