Ji-Cai Liu

The phosphorus mononitride (PN) molecule is of significant interest in both astrochemistry and fundamental chemical research. Conventional high-resolution spectral studies have predominantly emphasized the refinement of potential energy curves (PECs). In contrast, this study introduces a distinct perspective by highlighting the influence of the nuclear coordinate dependence ( R -dependence) of the transition dipole moments (TDMs) on spectral profiles. The strong R -dependence of the TDMs for selected electronic transitions is attributed to a change in the major orbital contributions, as visualized by the electron density difference maps. The R -dependent TDMs and the high-level ab initio PECs obtained using the explicitly correlated multireference configuration interaction (MRCI-F12) method are employed for vibronic spectra calculations using time-dependent wave packet methodology. To underline the influence of the non Franck–Condon (FC) effects, three theoretical methods of graded accuracy are compared, namely, FC approximation, FC approximation with Herzberg–Teller correction (FC-HT), and full coordinate dependence treatment of the TDM. We show that the conventional FC approximation breaks down completely for some valence transitions, where the FC-HT interference terms give significant contribution, suggesting that the full R -dependence of the TDM has to be taken into account for robust simulations of vibrationally resolved electronic spectra. This work provides a framework for accurately incorporating the R -dependence of the TDM in spectra calculations.

Multiply charged molecules fragment under Coulomb repulsion, leaving characteristic fingerprints in ensuing electronic decay. Using K-shell ionization of HCl as a benchmark, we identify metastable intermediates that persist to internuclear separations beyond 100 a.u., where weakened Coulomb interactions enable the emergence of narrow atomic lines, while short-lived states decay at smaller separations, producing broad, red-shifted backgrounds. This work provides a previously missing dynamical description of coupled electronic and nuclear evolution in the Coulomb fragmentation regime.

Interference between scattering channels is observed in resonant inelastic x-ray scattering (RIXS) at the Ne K threshold. Final states with | 2 p − 1 n p ⟩ as the main configuration are populated via | 1 s − 1 n ′ p ⟩ resonances, where large-amplitude one-electron ( n ′ = n ) channels interfere with small-amplitude two-electron ( n ′ ≠ n ) channels. The interference is manifested in an asymmetric line profile where the two-electron resonance occurs in the tail region of the one-electron resonance. In RIXS, this slowly varying tail plays the role of the continuum for the Fano effect. The asymmetric profile is well modeled by means of a single asymmetry parameter, determined by the amplitudes of the scattering channels and the energy separation between the resonances.

Different types of Young's double-slit experiments contain a significant amount of both particle and wave information running from full-particle to full-wave knowledge depending on the experimental conditions. We study the Young's double-slit interference in resonant Auger scattering from homonuclear diatomic molecules where opposite Doppler shifts for the dissociating atomic slits provide path information. Different quantitative formulation of Bohr's complementarity principle—path information vs interference—is applied to two types of resonant Auger scattering experiments, with fixed-in-space and randomly oriented molecules. Special attention is paid to the orientational dephasing in conventional Auger experiments with randomly oriented molecules. Our quantitative formulation of the complementarity is compared with the formulation made earlier by Greenberger and Yasin [D. M. Greenberger and A. Yasin, ]. Published by the American Physical Society 2024

Resonant inelastic x-ray scattering (RIXS) is a major method for investigation of electronic structure and dynamics, with applications ranging from basic atomic physics to materials science. In RIXS applied to inversion-symmetric systems, it has generally been accepted that strict parity selectivity applies in the sub–kilo–electron volt region. In contrast, we show that the parity selection rule is violated in the RIXS spectra of the free homonuclear diatomic O₂molecule. By analyzing the spectral dependence on scattering angle, we demonstrate that the violation is due to the phase difference in coherent scattering at the two atomic sites, in analogy with Young’s double-slit experiment. The result also implies that the interpretation of x-ray absorption spectra for inversion symmetric molecules in this energy range must be revised.

Structured light carrying orbital angular momentum (OAM) opens up a new physical dimension for studying light–matter interactions. Despite this, the complex fields created by OAM beams still remain largely unexplored in terms of their effects on surface plasmons. This paper presents a revelation of anomalous plasmon excitations in single particles and plasmon couplings of neighboring nanorods under OAM beams, which are forbidden using non-OAM sources. The plasmon excitation of single nanoparticles is determined both by photon spin angular momentum (SAM) and OAM and influenced by the locations of the nanoparticles. Specifically, when SAM and OAM are equal in magnitude and opposite in direction, a pure plasmon excitation along light propagation direction is achieved. Two plasmon dipoles show end-to-end antibonding coupling and side-by-side bounding coupling, which are the opposite of the typical couplings. Furthermore, we observe Fano resonance with a nanorod dimer: one aligned along light propagation direction acting as the bright mode and the other aligned along the global polarization direction of light acting as the dark mode, which is the opposite of the usual plasmonic Fano resonance. By taking advantage of the unique property of the OAM source, this investigation presents a novel way to control and study surface plasmons, and the research of plasmon behavior with OAM would open new avenues for controlling electromagnetic waves and enriching the spectroscopies with more degrees of freedom.

This work explores selective high-order resonances in asymmetric plasmonic nanoparticles stimulated by vortex beams. The results provide insights into controlling and understanding OAM-involved light-material interactions of asymmetric nanosystems.