Plasma and Fusion Research

Volume 21, 2401004 (2026)

Regular Articles

Observation of a 111.9 nm Narrow Spectral Line Emitted from Ne-Like Al Ion in Laser-Produced Plasmas
Yu TAKEHIRO1), Shusen GAO1), Yuito NISHII1), Maki KISHIMOTO1), Tomoyuki JOHZAKI1,2), Kotaro YAMASAKI1), Takeshi HIGASHIGUCHI3), Shinichi NAMBA1)
1)
Graduate School of Advanced Science and Engineering, Hiroshima University, Hiroshima 739-8527, Japan
2)
Institute of Laser Engineering, Osaka University, Osaka 565-0871, Japan
3)
Department of Electrical and Electronic Engineering, Utsunomiya University, Tochigi 321-8505, Japan
(Received 29 August 2025 / Accepted 21 October 2025 / Published 31 March 2026)

Abstract

Short-wavelength lasers based on a transient collisional excitation (TCE) have extensively been studied using neon (Ne)-like and nickel (Ni)-like ions. In this study, we have examined the possibility of amplified spontaneous emission (ASE) at 111.9 nm in a Ne-like aluminum (Al) plasma using the TCE scheme. Al targets in vacuum were irradiated with two time-delayed Nd:YAG laser pulses (wavelength: 1,064 nm). A pre-pulse laser generated a pre-formed plasma, and subsequently a grazing-incidence main-pulse laser axially heated it to excite 3p (1S0)–3s (1P1) transition of Al3+ ion. To achieve effective energy deposition in the region of electron density of ∼ 1018 cm−3, the main-pulse was introduced at 3.5° incidence angle. Under optimized conditions, a sharp spectral line at 111.9 nm, corresponding to the 3p–3s lasing transition in Ne-like Al ion, was observed. Although clear ASE was not observed, this work confirms the feasibility of vacuum ultraviolet (VUV) ASE generation by means of this scheme. Further improvements in pulse synchronization and irradiation conditions would show the prominent evidence of 111.9-nm ASE phenomenon.

Keywords

laser produced aluminum plasma, VUV laser, transient collisional excitation scheme

DOI: 10.1585/pfr.21.2401004

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