Experimental evidence of Langmuir-wave-caused features in spectral lines of laser-produced plasmas

The structures observed in profiles of the Lγ line of Al XIII emitted from the laser-produced plasma are identified as the Langmuir-wave-caused dips (L-dips). Hitherto, the L-dips were found in hydrogen and deuterium spectral lines only; we report the first experiment dedicated to their identification in higher-Z plasmas. The L-dip phenomenon has a fundamental importance as a nonlinear dynamic-resonance effect of essentially multifrequency nature. Besides, the L-dips can be practically used for measuring the amplitude of the Langmuir waves. The latter diagnostic application might be very important in future experiments with laser-produced plasmas, as no other method was suggested in the literature for this purpose yet.