The interaction of an ultra-short (<30 fs), high-contrast (<10⁻⁹), high-intensity (>10¹⁸ W cm⁻²) laser pulse with a solid target is not generally known to produce and accelerate negative ions. The transient accelerating electrostatic-fields are so strong that they ionize any atom or negative ion at the target surface. In spite of what may appear to be unfavourable conditions, here it is reported that H⁻ ions extending up to 80 keV are measured from such an interaction. The H⁻ ion flux is about 0.1% that of the H⁺ ions at 20 keV. These measurements employ a recently developed temporally-gated Thomson parabola ion spectrometry diagnostic which significantly improves signal-to-noise ratios. Electrons that co-propagate with the fast protons cause a two-step charge-reduction reaction. The gas phase three-body attachment of electrons to fast neutral hydrogen atoms accounts for the measured H⁻ yield. It is intriguing that such a fundamental gas-phase reaction, involving the attachment of an electron to a hydrogen atom, has not been observed in laboratory experiments previously. Laser-produced plasma offers an alternative environment to the conventional charged particle beam experiments, in which such atomic physics processes can be investigated.

通常不知道超短（<30 fs），高对比度（<10 ^-9），高强度（> 10 ¹⁸  W cm ^-2）激光脉冲与固体靶的相互作用会产生并加速负离子离子。瞬态加速静电场是如此之强，以至于它们使目标表面的任何原子或负离子电离。尽管可能会出现什么是不利条件下，在这里它被报告使得h ^-向上延伸离子到80keV的是从这样的相互作用进行测量。为H ^-离子通量是约0.1％，在H的⁺离子在20 keV下。这些测量使用最近开发的时间门控Thomson抛物线离子光谱诊断仪，可显着提高信噪比。与快速质子共传播的电子引起两步电荷还原反应。电子的气相三体附着到快速中性的氢原子占测量ħ ^-产率。令人感兴趣的是，以前在实验室实验中还没有观察到这种基本的气相反应，其中涉及电子与氢原子的连接。激光产生的等离子体为传统的带电粒子束实验提供了另一种环境，在其中可以研究此类原子物理过程。