Electronic spectroscopy of the jet-cooled arsenic dicarbide ( C 2 As ) free radical

• Published in: The Journal of chemical physics 2008-10, Vol.129 (13), p.134307-134307-7
• Main Authors: Wei, Jie, Grimminger, Robert A., Sunahori, Fumie X., Clouthier, Dennis J.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.2988311

The Δ r 2 - X ̃ Π r 2 band system of the jet-cooled arsenic dicarbide ( C 2 As ) free radical has been recorded by laser-induced fluorescence (LIF) techniques in the 685 - 588 nm region. The radical was produced in a pulsed electric discharge jet using a precursor mixture of As Cl 3 vapor and methane in high pressure argon. A series of weak bands involving all three excited state vibrations was observed for both C 2 12 As and C 2 13 As . High-resolution spectra of the Π 1 ∕ 2 2 component of the 0 0 0 bands of both isotopomers were rotationally analyzed, leading to the conclusion that the upper state is Δ 2 with a small spin-orbit splitting ( A = 2.78 cm − 1 ) . Ground and excited state molecular structures of r 0 ″ ( C C , ab initio ) = 1.2933 Å , r 0 ″ ( C As ) = 1.734 ( 4 ) Å and r 0 ′ ( C C , ab initio ) = 1.2276 Å , r 0 ′ ( C As ) = 1.830 ( 3 ) Å were derived from the B values and our density functional predictions of the C  C bond lengths. Single vibronic level emission spectra were recorded for many of the LIF bands and these were used to obtain the ground state vibrational frequencies and spin-orbit splittings. These data were satisfactorily fitted to a Renner-Teller model which gave C 2 12 As parameters of ε = 0.695 ( 8 ) , ω 1 = 1704.8 ( 20 ) cm − 1 , ω 2 = 161.6 ( 8 ) cm − 1 , ω 3 = 663.6 ( 12 ) cm − 1 , and a spin-orbit constant A = 857.7 ( 11 ) cm − 1 .