Observation of broadband ultraviolet emission from HG3

Abstract

A previously-unobserved emission continuum, peaking at $\sim$ 380 nm, has been observed when Hg vapor is photoexcited at 248 nm (KrF laser). Attributed to the mercury trimer, Hg$_{3}$, this emission continuum has a spectral breadth (FWHM) increased from $\sim$ 65 to $\sim$ 90 nm and a decay rate growed from $\sim 6 \times 10^3$ to $\sim 7 \times 10^3$ second$^{-1}$, corresponding to Hg vapor density rising from $\sim 10^{16}$ to $\sim 2 \times 10^{19}$ cm$^{-3}$. Comparisons of the observed spectra with theory \footnote{Kitamura, Hikaru. "Theoretical potential energy surfaces for excited mercury trimers." Chemical physics 325.2 (2006): 207-219.} suggest that continuum arises from transitions of the molecule of D$_{\infty h}$ symmetrical linear, D$_{3h}$ equilateral triangular and C$_{2h}$ equilateral triangular configurations.