High resolution continuous wave laser induced fluorescence spectroscopy of sputtered Zr atoms

Abstract

High resolution laser induced fluorescence(LIF)spectroscopy utilizing a continuous wave ring dye laser was used to measure the velocity distribution of sputtered Zr atoms. The ring dye laser permitted the determination of the sputtered Zr atom velocity distribution with a resolution of 2.4×103 cm/s over the emission range of 0 to 2×106 cm/s. The sputtered Zr atoms were produced by bombardment of the metal target by normally incident 3 keV Kr+. Determination of the velocity distributions was accomplished by tuning the exciting laser frequency through the Doppler shifted absorption frequencies of the sputtered atoms. It was determined that such processes as laser power density and transit time broadening of the sputtered atom’s energy levels, the laser pulse duration and bandwidth as well as the geometry of the fluorescence excitation and detection system were all critical parameters important to the understanding of the experimental LIFvelocity distributions. A comparison is also made between the use of cw and pulsed laser sources to excite the LIF emission. The measuredvelocity distributions were found to be in good agreement with previously proposed theoretical distributions based on the linear collision cascade model of sputtering.