Influence of laser polarization on X rays emission from low-density and high-density optical-field ionized plasmas in nitrogen

Abstract

Summary The origination of observed X-ray emissions are identified through looking for atomic spectra database lines data. From this observed ion stages, the peak intensity of femtosecond laser over a length of 3 mm of the gas cell can be deduced. We mainly present results of an experiment in which X-rays from an optical-field ionized (OFI) plasma driven by different polarized 34-mJ, 105-fs, 10-Hz Ti: sapphire laser system are generated under well-controlled conditions in a low-pressure gas cell (a gas cell filled with 0.266 KPa of Nitrogen) and in high gas density of the gas cell (a gas cell filled with 1.33 KPa of Nitrogen). Using Nitrogen as the medium, from X-rays emitted under well-controlled conditions of low-density plasmas driven by different laser polarization, we show many important features of the OFI process (the electron temperature for linear and circular light polarization, the generated ionization stages). From X-ray emissions at high gas density by different laser polarization, because of non-OFI process effects such as electron heating, collisional ionization and ionization defocusing, there is different optimum gas density value of the gas cell for different emitting spectrum line. The spectral line in which originated from C-like N ion show more intensity with linear than with circular polarization. The spectral line in which originated from B-like N ion gives a little more intensity with circular than with linear polarization. At the same time, we discuss and analyze that physical mechanisms may be responsible for these influences of laser polarization on X-rays emission from low-density and high-density optical-field ionized plasmas in Nitrogen.