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On subjecting either CS 2 or sulphur vapour in flowing neon to microwave discharge and collecting the products, we formed dilute deposits of S 2 + in solid Ne near 5 K. The photoluminescence of S 2 + in the system A 2 Π u → X 2 Π g was measured in the wavelength range 450–800 nm, and isotopically enriched samples of 34 S 2 + and 32 S 34 S + yielded unambiguous vibrational assignments; for 32 S 2 + up to v″ = 12, a ν 00 = (22260.8 ± 1.4) , Y ″ 1.0 = (809.0 ± 0.6) and Y ″ 2.0 = −(3.50 ± 0.04) cm −1 . In these photoluminescence spectra, two distinct progressions with separation insensitive to nuclear mass are observed, involving spin-orbital substates of the electronic ground state; the value of the spin-orbital coupling parameter A ″ 0 is (493 ± 2) cm −1 . Excitation spectra in the region 330–430 nm exhibited for 32 S 2 + a progression up to v′ = 15 with Y ′ 1,0 = (556.0 ± 0.4) and Y ′ 2,0 = −(3.21 ± 0.03) cm −1 . With improved resolution, the splitting of most lines into doublets or triplets is attributed to the effects of S 2 + in solid neon, being trapped in sites of multiple character. We compare our results for trapped 32 S 2 + with those reported for free 32 S 2 + in the gaseous phase, and discuss the spectral consequences of the confinement of species trapped by surrounding Ne atoms. |
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