Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 65(3): 113-118 (2016)


低圧の混合ガス試料(H2+CO, H2+CO2)中でのミュオン転移における化学効果Chemical Environmental Effects on Muon Transfer Process in Low Pressure Mixture Gases; H2+CO and H2+CO2

1大阪大学大学院理学研究科Graduate School of Science, Osaka University ◇ 560–0043 大阪府豊中市待兼山町1–1 ◇ 1–1 Machikaneyama, Toyonaka-shi, Osaka 560–0043, Japan

2日本原子力研究開発機構先端基礎研究センターAdvanced Science Research Center, Japan Atomic Energy Agency ◇ 319–1195 茨城県那珂郡東海村白方白根2–4 ◇ 2–4 Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki Pref. 319–1195, Japan

3高エネルギー加速器研究機構物質構造科学研究所Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) ◇ 305–0801 茨城県つくば市大穂1–1 ◇ 1–1 Oho, Tsukuba-shi, Ibaraki Pref. 305–0801, Japan

4高エネルギー加速器研究機構放射線科学センターRadiation Science Center, High Energy Accelerator Research Organization (KEK) ◇ 305–0801 茨城県つくば市大穂1–1 ◇ 1–1 Oho, Tsukuba-shi, Ibaraki Pref. 305–0801, Japan

5国際基督教大学教養学部College of Liberal Arts, International Christian University ◇ 181–8585 東京都三鷹市大沢3丁目10–2 ◇ 3–10–2 Osawa, Mitaka-shi, Tokyo 181–8585, Japan

受付日:2015年10月7日Received: October 7, 2015
受理日:2016年1月8日Accepted: January 8, 2016
発行日:2016年3月15日Published: March 15, 2016


A muonic hydrogen atom, which consists of a negative muon and a proton, behaves as an electrically neutral particle. As such, it can approach another nucleus without Coulomb repulsion, allowing the muon to be directly transferred to inner muon levels of the nucleus and form a muonic atom. We studied muonic atom formation via this muon transfer process in two chemical environments; CO and CO2 (CO has one oxygen atom and one triple bond, and CO2 has two oxygen and two double bond), to examine the effects of the environments on muonic atom formation. The muon capture probability and intensity pattern of muonic Xrays for carbon and oxygen atoms were determined through measurement of muonic Xrays emitted after muonic atom formation. By comparing the results of CO and CO2 to each other, we found that the muon capture probabilities and initial muon quantum levels for carbon and oxygen atoms resulting from the muon transfer process do not depend on the chemical environment, though a significant effect of the chemical environmental was observed for the direct muon capture process. The effect of the chemical environmental in muonic atom formation via the muon transfer process is too small to detect statistically significant in our experimental system.

Key words: muonic atom; muonic hydrogen; muon capture; muon transfer; muonic Xray; carbon oxide; low pressure gas

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