Vibrationally excited C4H

Rotational spectra in four new excited vibrational levels of the linear carbon chain radical C4H were observed in the millimeter band between 69 and 364 GHz in a low pressure glow discharge, and two of these were observed in a supersonic molecular beam between 19 and 38 GHz. All have rotational constants within 0.4% of the ground vibrational state of C4H and were assigned to new bending vibrational levels, two each with and vibrational symmetry. The new levels are tentatively assigned to the and bending vibrational modes (both with symmetry), and the and combination levels (symmetry) on the basis of the derived spectroscopic constants, relative intensities in our discharge source, and published laser spectroscopic and quantum calculations. Prior spectroscopic constants in the and levels were refined. Also presented are interferometric maps of the ground state and the level obtained with the Submillimeter Array (SMA) near 257 GHz which show that C4H is present near the central star in IRC+10216. We found no evidence with the SMA for the new vibrationally excited levels of C4H at a peak flux density averaged over a synthesized beam of Jy/beam in the 294-296 and 304-306 GHz range, but it is anticipated that rotational lines in the new levels might be observed in IRC+10216 when ALMA attains its full design capability.

Duke Scholars

Author Ken H Young Pathology