On the recombination heating of ultracold laser-produced plasmas

It is shown that the time dependences of the electron density measured by Kulin et al. (Kulin, S.D. et al., 2000, Phys. Rev. Lett., 85, 318) do not allow one to conclude whether three-body recombination occurs during the expansion of an ultracold laser-plasma plume. The assumption that recombination is suppressed is supported by the fact that no splash in the signal related to outgoing electrons was detected. Such a splash should be observed in the regime of recombination heating of plasma electrons.