			15min:

ASSIGNMENT OF THE MM- AND SMM-WAVE ROTATIONAL SPECTRA OF RARE ISOTOPOLOGUES OF CYANAMIDE AND THE r_m^(1) MOLECULAR GEOMETRY OF NH₂CN.

ADAM KRASNICKI, ZBIGNIEW KISIEL, Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa, Poland; BRENDA P. WINNEWISSER, MANFRED WINNEWISSER, Department of Physics, The Ohio State University, Columbus, OH 43210.

The cyanamide molecule is one of the prototype systems for the study of the large--amplitude inversion motion at the nitrogen atom, and it is also a potential astrophysical species. The mm-wave, smm-wave, and the far infrared spectra of the parent and the two principal deuterated isotopic species are now known in considerable detail.^,\footnoteZ.~Kisiel et al., 63^rd ~OSU~International~Symposium~on~Molecular~Spectroscopy, WK08, 2008.

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Presently we report an extended analysis of rotational transitions in the 0⁺ and 0^- inversion states for 7 rare isotopic species of cyanamide, measured in the 118-650 GHz frequency region on a deuterated sample with natural abundance of carbon and nitrogen. The spectra of five isotopologues: H₂N¹³CN, HDN¹³CN, D₂N¹³CN, HD¹⁵NCN, and HDNC¹⁵N, have been assigned for the first time. For D₂¹⁵NCN and D₂NC¹⁵N the knowledge of the rotational spectrum has also been considerably improved relative to preceding work.^,

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The availability of spectroscopic constants for 12 different isotopic species allowed determination of the complete r_m^(1) and r_m^(1 L) geometries of cyanamide, providing direct experimental information on the pyramidal nature of the NH₂ group in cyanamide and on the nonlinearity of the NCN segment. The new experimental geometry is compared with results of ab~initio calculations.