Time-resolved Fourier-transform infrared emission spectroscopy of Au in the1800–4000−cm−1region: Rydberg transitions

Abstract

Time-resolved Fourier-transform infrared spectroscopy was applied for observations of the emission arising after irradiation of a Au target with a pulsed nanosecond ArF ($\ensuremath{\lambda}=193$ nm) laser. A high-repetition-rate laser ($1.0$ kHz) with an output energy of $15$ mJ was focused on a rotating metal target inside a vacuum chamber (average pressure ${10}^{\ensuremath{-}2}$ Torr). The infrared emission spectra were observed in the $1800--4000{\mathrm{cm}}^{\ensuremath{-}1}$ spectral region with a time profile showing maximum emission intensity in $9--11$ $\ensuremath{\mu}$s after a laser shot. Seven prominent lines are reported; most of them are identified as being due to transitions between low Rydberg $\mathit{nl}$ states of Au with $n=5--10$ and $l=0--3$. An alternative identification ($6{f}_{5/2}\ensuremath{\rightarrow}7{d}_{3/2}$) is given for the $2518.489{\mathit{cm}}^{\ensuremath{-}1}$ line previously classified as $8{d}_{5/2}\ensuremath{\rightarrow}5{f}_{5/2}$. On the basis of the measured lines, three $f$ levels of the Au atom are reported and revised values are given for six other levels.