Spatio-temporal evolution of a nanosecond laser produced Zn plasma

Optical emission spectroscopy of a nanosecond (ns) laser produced plasma (LPP) is carried out to investigate the effects of irradiation energy and ambient pressure on the spatio-temporal evolution of the intensity and linewidth of emissions in an expanding plume. The linewidth of neutrals (δλn) increases as a function of pressure for all axial distances up to 4 mm from the target surface. The oscillating behavior of δλn upon increasing ambient pressure for femtosecond (fs) and picosecond (ps) LPPs in the pressure range of 0.5 Torr to 50 Torr is absent in the present case. Hence, the ambiguities in calculating the number density using δλn is invalid for ns LPPs.