MICROWAVE SPECTRUM OF 12 C 16 O S.A. TASHKUN and S.N. MIKHAILENKO, Laboratory of Theoretical Spectroscopy, V.E. Zuev Institute of Atmospheric Optics, Zuev square 1, , Tomsk, RUSSIA

Motivation Calculate microwave rotational transition frequencies with confidence intervals up to J = 50 for the 0-0, 1-1, 2-2, and 3-3 bands using experimental energy levels derived from measured transition frequencies Compare them with data in COLOGNE 1, JPL 2, NIST 3, and HITRAN 4 databanks 1) H.S.P. Muller et al, J Mol Struct –227 (2005) 2) H.M. Pickett et al, JPL Catalog (2000), spec.jpl.nasa.gov 3) F.J. Lovas, 4) L.S. Rothman et al, JQSRT, 110, 553 (2009)

Experimental energy levels Measured transition frequencies and measurement uncertainties collected from the literature Ritz computer code

Derivation of energy levels Ideally: In reality: More detail in S.A. Tashkun et al JQSRT 111, 1106 (2010) c s – correction factors for some spectra (for microwave spectra c s =0) - measurement uncertainty - pressure induced shift Finally: c s, {E} are unknowns Portrait of the correlation matrix Values and uncertainties of experimental energy levels N tra = N lev = 2247 Χ = 0.71

assign RITZ(MHz) unc(KHz) COLOGNE(MHz) unc(KHz) JPL(MHz) unc(KHz) NIST(MHz) unc(KHz) Pure rotational spectrum Blue – measured frequencies; red – calculated frequencies

Pure rotational spectrum (extrapolation) assign RITZ(MHz) unc(KHz) JPL(MHz) unc(KHz) RITZ - JPL(KHz) Energy levels: E 0,49 = ± cm -1 Ntra = 6 Refs: a b c d e f E 0,48 = ± cm -1 Ntra = 10 Refs: a b c d e f g a 1.0 R. Farrenq et al, JMS 149, 375 (1991); FT/solar absorption filter 2 b R. Farrenq et al, JMS 149, 375 (1991); FT/solar absorption filter 3 c R. Farrenq et al, JMS 149, 375 (1991); FT/solar absorption filter 4 d 1.0 G. Guelachvili et al, JMS 98, 64 (1983) FT/set C e 1.0 A.W. Mantz and J.P. Maillard, JMS 53, 466 (1974); FT/emission f D.H. Rank et al, JMS 18, 418 (1965) g D.H. Rank et al, JMS 4, 518 (1960) Consider:

F.J. Lovas, NIST recommended rest frequencies for observed inter- stellar molecular microwave transitions-2002 revision. J. Phys. Chem. Ref. Data, 33, 177 (2004)

RITZ vs HITRAN-2008 Residuals Uncertainties zoom 100 microwave transitions spectral range 3.8 – cm -1 intensity range cm/molecule position uncertainty – cm -1

Conclusions Microwave transition frequencies of the 0-0,1-1,2-2, and 3-3 bands up to J=50 calculated from experimental energy levels * were presented. Each frequency is given together with 99% confidence interval. A comparison of calculated data and data from COLOGNE, JPL, NIST, and HITRAN databanks revealed a number of discrepancies which should be removed in future releases of these databanks *) S.A. Tashkun et al JQSRT 111, 1106 (2010)

Financial support We acknowledge support from a joint RFBR ( ИК_а) and CRDF (RUG TO-09) grant.