Analysis of the M-shell spectra emitted by a short-pulse laser-created tantalum plasma

The spectrum of tantalum emitted by a subpicosecond laser-created plasma, was recorded in the regions of the [Formula Presented] [Formula Presented] and [Formula Presented] transitions. The main difference with a nanosecond laser-created plasma spectrum is a broad understructure appearing under the [Formula Presented] transitions. An interpretation of this feature as a density effect is proposed. The supertransition array model is used for interpreting the spectrum, assuming local thermodynamic equilibrium (LTE) at some effective temperature. An interpretation of the [Formula Presented] spectrum using the more detailed unresolved transition array formalism, which does not assume LTE, is also proposed. Fitted contributions of the different ionic species differ slightly from the LTE-predicted values.