High Resolution Spectroscopy of Laser-Produced Lanthanide Plasmas and Investigations of High Harmonic Radiation

Laser-produced plasmas are well established as a source of ions for spectroscopy with practical applications in extreme ultraviolet lithography and soft x-ray microscopy, while more recently high order harmonic generation from relativistically driven laser-plasma interaction has shown the ability to become a reliable a source of intense, isolated attosecond pulses. This thesis first explores laser-produced plasmas of rare-earth elements. Spectra of cerium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, yttrium and lutetium were recorded individually between 1 and 10 nm at power densities ranging from 2x10^{10} W cm^{-2} - 2x10^{13} W cm^{-2}. Calculations were made using the Cowan code to obtain the predicted wavelengths and strengths of expected electron transitions from ions with either open 4d or open 4f shells. The trends in the spectra of the rare-earth elements were examined and a more detailed analysis was completed on the spectra of cerium. An unresolved transition array (UTA) formed from 4d-4f transitions was confirmed to dominate each spectrum. In cerium and samarium two distinct components of the UTA were observed whose appearance was strongly dependent on laser power density, corresponding to transitions involving ions with open 4d and open 4f subshells, the latter at longer wavelengths. Multiple other transition arrays were identified and UTA statistics were given for those identified in the cerium spectra. A double optical gating scheme, combining polarisation gating with a second harmonic, has the potential to make isolated attosecond pulses available on a wider scale by allowing for the use of longer duration driving pulses. Particle-in-Cell simulations were performed to investigate the effect of varying the carrier envelope phase and the relative phase of the second harmonic on the attosecond pulses produced using the double optical gating scheme with a 10 fs driving pulse. The variation of both the carrier envelope phase and the relative phase of the second harmonic was found to effect both the isolation and intensity of the resultant attosecond pulses. Optimising the phases leads to excellent isolation and intensity compared to polarisation gating alone.