The smallest polyatomic carbon chain, C 3 , has been identified in interstellar clouds (A v ∼1 mag) towards ζ Ophiuchi, 20 Aquilae, and ζ Persei by detection of the origin band in its A 1 Π u − X 1 Σ + g electronic transition, near 4052 Å. Individual rotational lines were resolved up to J=30 enabling the rotational level column densities and temperature distributions to be determined. The inferred limits for the total column densities (∼1 to 2×10 12 cm −2 ) offer a strong incentive to laboratory and astrophysical searches for the longer carbon chains. Concurrent searches for C + 2 , C − 2 and C − 3 were negative but provide sensitive estimates for their maximum column densities.

High resolution study of spin-orbit mixing and the singlet-triplet gap in chlorocarbene: Stimulated emission pumping spectroscopy of CH 35 Cl and CD 35 Cl Electronic states of linear polyenes: High resolution spectroscopy of cis-and trans-1,3,5,7,9-decapentaene J. Chem. Phys. 108, 9586 (1998); 10.1063/1.476407 Solvation dynamics and electronic structure development of coumarin 120 in methanol: A theoretical modeling studyThe optothermal technique has been utilized to obtain the first high resolution spectrum of pyridine in the region of the S 1 ←S 0 electronic transition. Rotational profiles for several vibronic bands (0 0 0 ,6a 0 1 ,16b 0 2 6a 0 1 ,6a 0 2 ,12 0 1 ) were measured and found to be severely homogeneously broadened with linewidths of the order of 3-5 GHz, in agreement with previous lifetime measurements. Rotational constants of pyridine in the excited S 1 vibronic levels were extracted by a band contour analysis. The values obtained are in good agreement with results from ab initio calculations, also presented here.

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