Barely fluorescent molecules. I. Twin-discharge jet laser-induced fluorescence spectroscopy of HSnCl and DSnCl

The divalent tin transient molecules HSnCl and DSnCl have been detected for the first time by laser-induced fluorescence (LIF) spectroscopy. HSnCl/DSnCl were produced in a twin-discharge jet using separate precursor streams of SnH₄/SnD₄ and the discharge products from HCl/DCl, both diluted in high pressure argon. The ùA″-X̃¹A' spectrum of HSnCl consists of a single vibronic 0₀ ⁰ band with a very short fluorescence lifetime (∼30 ns). In contrast, the LIF spectrum of DSnCl exhibits three bands (0₀ ⁰,2₀ ¹,and2₀ ²), whose fluorescence lifetimes decrease from 393 ns (0⁰) to less than 10 ns (2²). Single vibronic level emission spectra have been recorded, providing information on all three vibrational modes in the ground state. Previous detailed ab initio studies indicate that these molecules dissociate into SnCl + H on the excited state potential surface and this is the cause of the short fluorescence lifetimes and breaking off of the fluorescence. It is fortunate that the HSnCl excited state zero-point level is still fluorescent or it would not be detectable by LIF spectroscopy.