Production of an extremely cold plasma by optical-field-induced ionization

We report the production of an extremely cold lithium plasma by optical-field-induced ionization. Such a cold plasma was realized by irradiating a 0.5-ps KrF laser focused into a singly ionized lithium plasma at an intensity of ${10}^{17}$ W ${\mathrm{cm}}^{\mathrm{-}2}$. An average electron temperature of less than 1 eV was estimated by measuring the intensity ratio of the Lyman series line emission in a hydrogenlike lithium plasma. The time history of the Lyman-α laser (13.5 nm) in a lithium plasma strongly ensures the production of an extremely cold plasma.