[摘要]：The interaction between a metastable H(2s) atomic hydrogen beam and an external electric field leads to the emission of the Lyman-alpha line. It originates in the Stark mixing of the near-degenerate 2s(1/2) and 2p(1/2) levels separated by the Lamb shift. The quenched radiation proportional to the square of the electric field amplitude is recovered in vacuum by using such an atomic probe beam. We observe the strong enhancement of the signal when the field is oscillating at the Lamb shift frequency. This technique is applied in a plasma, offering an alternative way to measure weak electric fields by direct and non-intrusive means. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3658459]
