Heavy N+ ion transfer in doubly charged N2Ar van der Waals cluster

Tunnelling of electrons via the neighboring atom

As compared to the intuitive process that the electron emits straight to the continuum from its parent ion, there is an alternative route that the electron may transfer to and be trapped by a neighboring ionic core before the eventual release. Here, we demonstrate that electron tunnelling via the neighboring atomic core is a pronounced process in light-induced tunnelling ionization of molecules by absorbing multiple near-infrared photons. We devised a site-resolved tunnelling experiment using an Ar-Kr+ ion as a prototype system to track the electron tunnelling dynamics from the Ar atom towards the neighboring Kr+ by monitoring its transverse momentum distribution, which is temporally captured into the resonant excited states of the Ar-Kr+ before its eventual releasing. The influence of the Coulomb potential of neighboring ionic cores promises new insights into the understanding and controlling of tunnelling dynamics in complex molecules or environment.

Development of a cold target recoil ion momentum spectrometer and a projectile charge state analyzer setup to study electron transfer processes in highly charged ion-atom/molecule collisions

We report the development and performance of a cold target recoil ion momentum spectrometer (COLTRIMS) setup at TIFR, which is built to study various atomic and molecular processes involving the interaction of slow, highly charged ions from an electron cyclotron resonance based ion accelerator. We give a detailed description of the experimental setup, as well as report some initial results on the electron-capture process in collisions of Ar⁸⁺ ions with helium and carbon monoxide targets. Here, we present the longitudinal momentum transfer and the sub-shell resolved Q-value spectrum in the case of 2, 4, and 6 keV/u Ar⁸⁺ beams in collision with helium. A longitudinal momentum resolution of 0.27 a.u. is achieved in the present system. We also report the state-selective scattering angle distributions for all the collision systems under investigation. We further discuss the fragmentation of the CO²⁺ molecular ions for different electron capture channels for the 5 keV/u Ar⁸⁺ beam. The combination of the COLTRIMS, along with the beam cleaner, the electrostatic deflectors, and the charge state analyzer, is shown to have certain advantages.

Femtosecond Time-Resolved Neighbor Roles in the Fragmentation Dynamics of Molecules in a Dimer

How the neighbor effect plays its role in the fragmentation of molecular clusters attracts great attention for physicists and chemists. Here, we study this effect in the fragmentation of N_{2}O dimer by performing three-body coincidence measurements on the femtosecond timescale. Rotations of bound N_{2}O^{+} triggered by neutral or ionic neighbors are tracked. The forbidden dissociation path between B^{2}Π and ^{4}Π is opened by the spin-exchange effect due to the existence of neighbor ions, leading to a new channel of N_{2}O^{+}→NO+N^{+} originating from B^{2}Π. The formation and dissociation of the metastable product N_{3}O_{2}^{+} from two ion-molecule reaction channels are tracked in real time, and the corresponding trajectories are captured. Our results demonstrate a significant and promising step towards the understanding of neighbor roles in the reactions within clusters.

Light-Induced Ultrafast Molecular Dynamics: From Photochemistry to Optochemistry

By precisely controlling the waveform of ultrashort laser fields, electronic and nuclear motions in molecules can be steered on extremely short time scales, even in the attosecond regime. This new research field, termed "optochemistry", presents the light field in the time-frequency domain and opens new avenues for tailoring molecular reactions beyond photochemistry. This Perspective summarizes the ultrafast laser techniques employed in recent years for manipulating the molecular reactions based on waveform control of intense ultrashort laser pulses, where the chemical reactions can take place in isolated molecules, clusters, and various nanosystems. The underlying mechanisms for the coherent control of molecular dynamics are explicitly explored. Challenges and opportunities coexist in the field of optochemistry. Advanced technologies and theoretical modeling are still being pursued, with great prospects for controlling chemical reactions with unprecedented spatiotemporal precision.