Yonggang Yang

We design laser pulses to transform the oriented model formic acid (HCOOH) from its achiral ground state ( A ′ ) to chiral configurations in the first excited state ( A ′ ′ ). Optimal control of the production of the target enantiomer followed by enantiomer flips with highest enantiomeric excess is achieved by means of a linearly polarized laser pulse with optimal duration, field strength, frequency, and direction of polarization. The approach is motivated by effects of directionality of x-ray or laser pulses on different aspects of chirality of HCOOH discovered by the team of Dörner using cold target recoil ion momentum spectroscopy.

Charge migration in molecular ions arises from the complex interplay between electronic dynamics and nuclear motion, with decoherence and recoherence playing pivotal roles in spatiotemporal evolution of this process. In this work, we present a detailed theoretical study of charge migration in the ionized 1-iodo-1,3-butadiyne cation using ab initio quantum dynamics simulations. We analyze ultrafast charge migration along the molecular axis and quantify the nuclear wave packet overlap between the electronic ground and first excited states to elucidate the mechanisms underlying decoherence and recoherence. Our results reveal that only a few symmetry-preserving vibrational normal modes significantly influence the coherence dynamics. Furthermore, we show that nonadiabatic transitions and spin–orbit coupling have minimal impact on the core coherence evolution of charge migration in IC4H+.

Time-resolved X-ray absorption spectroscopy is a widely used technique for monitoring ultrafast dynamics of molecules. Here we use this technique to analyze the quantum nuclear dynamics of NaK molecules in the first excited state. To quantitatively reconstruct the vibrational dynamics, we introduce a similarity function to determine the time-dependent position of the nuclear wavepacket from the time-resolved X-ray absorption spectroscopy. Here we demonstrate this new approach through numerical simulations.

A new and concise method to obtain the eigenvalues and eigenfunctions of a two-dimensional rotational–torsional Hamiltonian with correct boundary conditions is proposed for oriented AXn1-BYn2 type molecules. The corresponding eigenfunctions are not only eigenfunctions of the Hamiltonian but also common eigenfunctions of several symmetry operators. Numerical calculations for the lowest 1000 rotational–torsional eigenstates of BF2BCl2 demonstrate the advantages and applicability of our method.

The vibronic ground state of HO–H–OH− represents axial Ra and Sa enantiomers, with equal probabilities. It can be prepared thermodynamically at low temperatures (4K). If the chirality is measured to be Ra, then wavefunction collapse induces periodic quantum stereo-mutation from Ra to Sa to Ra to Sa and so on. Similarly, the observation of Sa induces chirality flips from Sa to Ra to Sa to Ra and so on. The period of stereo-mutation is τ = 2.554 ps. The phenomenon is supported by the low energy barrier 174.6 hc cm−1 between the enantiomers and by the light masses of the hydrogen atoms, which interchange positions during stereo-mutation. Interchanges of heavier atoms and higher energy barriers would prohibit Schrödinger cat ground states. This is demonstrated for the counter example, isotopically substituted 12CDH13CH2–Si–12C13C. The results are obtained by means of quantum chemical calculations and quantum dynamics simulations.

A key goal of ultrafast science is to pursue long-lived electronic coherences during molecular processes. The electronic coherence during charge migration can be characterized by the strength of the electronic flux. We report the size dependence of the de- and recoherences of charge migration in H ( CC ) n Cl + by systematic quantum dynamics simulations for n = 1 – 4 . The result is counterintuitive, namely the overall extent of electronic coherence increases with molecular size. Charge migration in the longest ions lasts for more than 100 fs, while it stops at about 10 fs in many previously investigated molecules.

Recently it has been shown that two coincident well designed laser pulses with two different combinations of circular polarizations ( or ) can create chiral electronic densities in an oriented heteronuclear diatomic molecule. Subsequently, the chirality flips from the electronic R_a to S_a to R_a to S_a etc. enantiomers, with periods in the femtosecond (fs) and attosecond (as) time domains. The results were obtained by means of quantum dynamics simulations for oriented NaK. Here we investigate the electronic chirality flips in oriented RbCs induced by all possible ( , , , ) combinations of circular polarizations of two coincident well‐designed laser pulses. Accordingly, the and as well as the and combinations generate opposite electronic enantiomers, e. g. R_a versus S_a, followed by opposite periodic chirality flips, e. g. from R_a to S_a to R_a to S_a etc. versus from S_a to R_a to S_a to R_a etc, with periods in the fs and as time domains, respectively. The laser induced spatio‐temporal symmetries are derived from first principles and illustrated by quantum dynamics simulations.