The emission spectrum of the SiCI+ radical cation, excited by the thermal energy He+ + SiCI, reaction, has been observed and vibrationally analyzed in the 310-350nm region. The two new subband systems, ci3II0+-XIZ+ and 03n,-XIZ+, have been identified.The vibrational assignments were confirmed by the observed isotope band heads of Si35CI+ and Si37CI+. The following molecular constants (in c m l ) have been obtained for the X I Z + , a3110+, and ci311, states. c i 3 n , : T , = 3 1 8 3 6 f 3 ; 0 , = 5 9 6 . 0 f 1 . 8 ; o C x , = 6 . 7 5 f 0 . 5 6 a3n0+: T , = 31 721 + 2 ; o , = 595.8 + l.o:o,s, = 6.62 * 0.12 XIZ+: o, = 680.8 k 0.6; o,x, = 2.57 zk 0.05 -Le spectre d'emission du radical libre charge positivement SiCI+, excite par la reaction d'energie thermique He+ + SiCI, a eteobserve et a fait I'objet d'une analyse vibrationnelle dans la region 310-350nm. On a identifie deux nouveaux systemes de sous-bandes, a3no+-XIZ+ et a3n,-XIZ+.Les assignations vibrationnelles ont ete confirmees par les observations relatives aux differences isotopiques entre les tstes de bandes de Si3SCI+ et SP7C1+. On a obtenu, pour les etats X I Z + , a 3 n o + et a3111, les valeurs suivantes des constantes moleculaires, en cm -I . a 3 n , : T,= 31 836 f 3 ; o , = 596.0 f 1,8;o,x, = 6.75 f 0.56 a3110+: T , = 31 721 + 2; o, = 595,8 f 1.0; o,x, = 6.62 + 0.12 XIZ+: o, = 680.8 f 0.6; o,x, = 2,57 + 0.05 [Traduit par le journal] Can. J . Phys.. 59.985 (1981)