Spectroscopy of positronium molecules and Bose-Einstein Condensates

正电子分子和玻色-爱因斯坦凝聚态的光谱学

• 批准号: 0555701
• 负责人: Allen Mills
• 金额: --
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-15 至 2010-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0555701&HistoricalAwards=false
• 关键词: Spectroscopy; positronium; molecules; Bose; Einstein

Positronium, with the chemical symbol Ps, is a very light form of hydrogen atom consisting of an electron and an anti-electron, or positron. Being composed of equal amounts of matter and antimatter, the longest-lived ground state of positronium lives for only one seventh of a microsecond before annihilating into three photons. Nevertheless, this transient existence is long enough for studying the properties of a dense gas of positronium atoms. This research will employ a dense positronium gas to investigate di-positronium molecules, Ps2, and positronium Bose-Einstein condensation. An apparatus developed with the assistance of an NSF Instrumentation program grant (DMR-0216927) will provide this project with short pulses containing about 100 million positrons. The positrons will be focused on a target surface composed of a porous solid in which positronium atoms form with high probability. The target will contain a tiny buried cavity into which one million positronium atoms will collect to a density such that positronium Bose-Einstein condensation should occur at temperatures as high as 20K. To observe these effects, a pulsed laser system will deliver ultra-violet light capable of exciting the positronium and Ps2 Lyman-alpha, or ground-state to first excited state, transitions. Although a Ps cavity would be transparent to the ultra-violet light when filled with an ordinary gas of positronium atoms, the cavity will become opaque when the atoms condense, thus enabling the first observations of positronium Bose-Einstein condensation. The broader impact of the program involves student training as well as outreach to the local high school.

正电子素，化学符号Ps，是一种非常轻的氢原子形式，由一个电子和一个反电子或正电子组成。正电子素由等量的物质和反物质组成，最长寿命的基态在湮灭成三个光子之前只存在七分之一微秒。然而，这种短暂的存在对于研究正电子素原子的致密气体的性质来说已经足够长了。这项研究将采用稠密的正电子素气体来研究双正电子素分子，Ps2和正电子素玻色-爱因斯坦凝聚。在NSF仪器计划资助（DMR-0216927）的帮助下开发的设备将为该项目提供包含约1亿个正电子的短脉冲。正电子将聚焦在由多孔固体组成的靶表面上，在多孔固体中，正电子素原子以高概率形成。目标将包含一个微小的掩埋腔，其中将收集一百万个正电子素原子，其密度使得正电子素玻色-爱因斯坦凝聚应该在高达20 K的温度下发生。为了观察这些效应，脉冲激光系统将提供能够激发正电子素和Ps2莱曼-α（或基态到第一激发态）跃迁的紫外光。虽然Ps腔在充满正电子素原子的普通气体时对紫外线是透明的，但当原子凝聚时，腔将变得不透明，从而使正电子素玻色-爱因斯坦凝聚的第一次观测成为可能。该计划的更广泛影响包括学生培训以及与当地高中的联系。