Detection and characterization of the tin dihydride (SnH₂ and SnD₂) molecule in the gas phase

The SnH₂ and SnD₂ molecules have been detected for the first time in the gas phase by laser-induced fluorescence (LIF) and emission spectroscopic techniques through the ùB₁-X̃¹A₁ electronic transition. These reactive species were prepared in a pulsed electric discharge jet using (CH₃)₄Sn or SnH₄/SnD₄ precursors diluted in high pressure argon. Transitions to the electronic excited state of the jet-cooled molecules were probed with LIF, and the ground state energy levels were measured from single rovibronic level emission spectra. The LIF spectrum of SnD₂ afforded sufficient rotational structure to determine the ground and excited state geometries: r₀^″ = 1.768 Å, θ₀^″ = 91.0°, r₀^' = 1.729 Å, θ₀^' = 122.9°. All of the observed LIF bands show evidence of a rotational-level-dependent predissociation process which rapidly decreases the fluorescence yield and lifetime with increasing rotational angular momentum in each excited vibronic level. This behavior is analogous to that observed in SiH₂ and GeH₂ and is suggested to lead to the formation of ground state tin atoms and hydrogen molecules.