arXiv subjects

Yoshiro Azuma

Publications and source records attributed to Yoshiro Azuma.

3 recordsLinked to original sources

arXiv2025

Scattering Angle Dependence of Fano Resonance Profiles in Cold Atomic Collisions Analyzed with the Complex Valued $w$ Parameter

The scattering angle dependence of Fano resonance profiles in cold atomic collisions has been theoretically studied. A complex-valued parameter $ w $ with an analytical formula describing the asymmetry of the resonance profile is proposed as a new development from previous work on electron resonance scattering from atoms [F. Koike, J. Phys. $\mathbf{B10}$, 2883 (1977)]. It serves as the general formulation which leads to the angle-dependence of Fano's $ q $ parameter. Calculations for the case of cold elastic collisions of hydrogen atoms with krypton atoms have been accomplished. The strong angle dependence of the resonance profile asymmetry in the differential scattering cross section due to the interference with non-resonant partial waves is demonstrated. The scattering angle dependence of the resonance profile and thus the newly proposed asymmetry parameter is highly sensitive to the inter-atomic interaction potentials. This is likely to prove useful for the study of interaction potentials themselves.

physics.atom-ph↗

arXiv2021

The quantum and classical Fano parameter $q$

The Fano resonance has been a familiar and important feature in atomic and molecular physics for more than half a century. Typically, the combination of a discrete state with one or more continua results in an asymmetric peak in the ionization spectrum. The peak-shape, called the Fano profile, can be expressed by a simple formula derived by Fano in 1935. However, the interpretation of its characteristic parameter $q$, which represents the asymmetry of the peak in the formula, is not necessarily intuitively transparent. The Fano resonance is not necessarily a quantum effect, but it is a manifestation of a certain physical mechanism in various systems, both quantum and classical. Through the derivation of $q$ from the known classical pictures with the classical coupled oscillator, we interpret the $q$ value with a geometrical view. And further, we introduce a complex valued $q$ parameter for the description of the resonance with a damped oscillator.

physics.atom-ph↗

arXiv2018

Superfluorescence, free-induction decay, and four-wave mixing: propagation of free-electron laser pulses through a dense sample of helium ions

We report an experimental and numerical study of the propagation of free-electron laser pulses (wavelength 24.3 nm) through helium gas. Ionisation and excitation populates the He$^{+}$ 4$p$ state. Strong, directional emission was observed at wavelengths of 469 nm, 164 nm, 30.4 nm, and 24.5 nm. We interpret the emissions at 469 nm and 164 nm as 4$p$-3$s$-2$p$ cascade superfluorescence, that at 30.4 nm as yoked superfluorescence on the 2$p$-1$s$ transition, and that at 25.6 nm as free-induction decay of the 3$p$ state.

physics.atom-ph↗