Threshold photodetachment spectroscopy of the positronium negative ion has been accomplished for the first time employing an efficient source of the ions and photodetachment techniques combined with a tunable optical parametric oscillator and amplifier laser. The photodetachment threshold, corresponding to the electron affinity of positronium ($1{{}^{3}S}_1$), was determined to be $326.88\pm 0.09(\mathrm{stat})\pm 0.10(\mathrm{syst})\mathrm{meV}$ by laser photodetachment threshold measurements. This result is consistent with a variational calculation corrected for leading relativistic and quantum electrodynamical effects.

中文翻译：

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正电子负离子的阈值光解谱。

负离子的阈值光解谱技术是首次采用有效的离子源和光解技术与可调谐光学参量振荡器和放大器激光器相结合而实现的。光脱离阈值，对应于正电子的电子亲和力（$\mathrm{1个}{{}^3\mathrm{小号}}_{\mathrm{1个}}$），确定为 $326.88\pm 0.09（\mathrm{统计}）\pm 0.10（\mathrm{系统}）\mathrm{病毒}$通过激光光解阈值测量。该结果与针对领先的相对论和量子电动力学效应而校正的变分计算相一致。