The pure rotational and rotationndash;vibrational Raman spectra of cyanogen, C2N2, were photographed under high resolution. The spectra were excited with a single mode argon laser operating at lgr;=4880 Aring;. The pure rotation spectrum shows a partially resolved hot band structure that is assigned to the ngr;51and 2ngr;5vibrationally excited states. Thelhyphen;type doubling in the pure rotational spectrum of molecules in the ngr;15state is sufficiently well resolved at highJvalues to allow a determination of thelhyphen;type doubling constant. The ngr;1(Sgr;+g) and ngr;14(Pgr;g) fundamental rotationndash;vibration bands were also photographed. Both fundamentals are overlapped by vibrational hot bands originating in lowhyphen;lying vibrational levels. Molecular constants obtained in the present work are, in units of cmminus;1, The constants for the ngr;15and 2ngr;50,2states were obtained from the pure rotation spectrum. The vibrational constants were found to be The ground state constantsB0andD0and their uncertainties were determined by an extrapolation procedure. For all other constants the quoted errors are one standard deviation and only represent the internal errors generated in the least squares analysis of the data. Vibrational constants determined fromQhyphen;branch measurements only are indicated by (Q).
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