Molecular photoelectron angular distribution rotations in multi-photon resonant ionization of H2+ by circularly polarized ultraviolet laser pulses

Unveiling Coherent Control of Halomethane Dissociation Induced by a Single Strong Ultraviolet Pulse

We present a theoretical investigation into the coherent control of photodissociation reactions in halomethanes, specifically focusing on CH2BrCl by manipulating the spectral phase of a single femtosecond laser pulse. We examine the photodissociation of CH2BrCl under an ultrashort pulse with a quadratic spectral phase and reveal the sensitivity of both the total dissociation probability and the resulting radical products (Br+CH2Cl and Cl+CH2Br) to chirp rates. To gain insights into the underlying mechanism, we calculate the population distributions of excited vibrational states in the ground electronic state, demonstrating the occurrence of resonance Raman scattering (RRS) in the strong-field limit regime. By utilizing chirped pulses, we show that this RRS phenomenon can be suppressed and even eliminated through quantum destructive interference. This highlights the high sensitivity of photodissociation into Cl+CH2Br to the spectral phase, showcasing a phenomenon that goes beyond the traditional one-photon photodissociation of isolated molecules in the weak-field limit regime. These findings emphasize the importance of coherent control in the exploration and utilization of photodissociation in polyatomic molecules, paving the way for new advancements in chemical physics and femtochemistry.

Controlling the atomic-orbital-resolved photoionization for neon atoms by counter-rotating circularly polarized attosecond pulses

We theoretically investigate the atomic-orbital-resolved vortex-shaped photoelectron momentum distributions (PMDs) and ionization probabilities by solving the two-dimensional time-dependent Schrödinger equation (2D-TDSE) of neon in a pair of delayed counter-rotating circularly polarized attosecond pulses. We found that the number of spiral arms in vortex patterns is twice the number of absorbed photons when the initial state is the ψ_m=±1 state, which satisfy a change from c_2n+2 to c_2n (n is the number of absorbed photons) rotational symmetry of the vortices if the 2p state is replaced by 2p₊ or 2p_- states. For two- and three-photon ionization, the magnetic quantum number dependence of ionization probabilities is quite weak. Interestingly, single-photon ionization is preferred when the electron and laser field corotate and ionization probabilities of 2p_- is much larger than that of 2p₊ if the proper time delay and wavelength are used. The relative ratio of ionization probabilities between 2p_- and 2p₊ is insensitive to laser peak intensity, which can be controlled by changing the wavelength, time delay, relative phase and amplitude ratio of two attosecond pulses.

Attosecond Dynamics of Molecular Electronic Ring Currents

Ultrafast charge migration is of fundamental importance to photoinduced chemical reactions. However, exploring such a quantum dynamical process requires demanding spatial and temporal resolutions. We show how electronic coherence dynamics induced in molecules by a circularly polarized UV pulse can be tracked by using a time-delayed circularly polarized attosecond X-ray pulse. The X-ray probe spectra retrieve an image at different time delays, encoding instantaneous pump-induced circular charge migration information on an attosecond time scale. A time-dependent ultrafast electronic coherence associated with the periodical circular ring currents shows a strong dependence on the helicity of the UV pulse, which may provide a direct approach to access and control the electronic quantum coherence dynamics in photophysical and photochemical reactions in real time.

Toward the Full Quantum Dynamical Description of Photon Induced Processes in D2. J Phys Chem A 2016;120:9411-9421. [PMID: 27934332 DOI: 10.1021/acs.jpca.6b09623]

The dissociative ionization (multiphoton regime) of the D₂⁺ ion by ultrashort laser pulses has been studied theoretically using ab initio calculations. The combined ionization and dissociation spectrum was explored for fixed molecular axis orientations. In accordance with previous investigations, the dominant features in the obtained joint energy spectrum were multiphoton peaks. In addition to this, in the present work, photoelectron angular distributions were analyzed as well. By performing a partial wave analysis for each multiphoton peak, we have identified the number of absorbed photons. Moreover, we also found that the angular distribution can significantly change inside a multiphoton peak as a function of electron and nuclear kinetic energy.