Thebtilde;1B1larr;atilde;thinsp;1A1spectrum of CH2radical has been recorded with Dopplerhyphen;limited resolution in the 15thinsp;600ndash;18thinsp;650 cmminus;1wavelength region by laser flashhyphen;kinetic absorption spectroscopy. Singlet methylene is produced by photolysis of ketene at 308 nm. Assignments for 477 transitions originating from1A1(0,0,0) and (0,1,0) levels withJle;8 andKale;5 are reported from some 10thinsp;000 lines observed. Term values are given for these1A1levels and1B1(0,v2,0) levels with 13le;v2le;17. Magnetichyphen;rotation signals were observed for 60percnt; of the 424 lines studied. This anomalous Zeeman effect is explained by singletndash;triplet mixing in bothatilde; andbtilde; states. Extensive singletndash;triplet mixing occurs for1B1levels withKane;0; this mixing is allowed in second order by Rennerndash;Teller coupling ofbtilde;thinsp;1B1withatilde;thinsp;1A1and by spinhyphen;orbit coupling viaatilde;thinsp;1A1toXtilde;thinsp;3B1. The consequent shifts prevent determination of accurate rovibrational structural parameters for the1B1state.
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