Vibrationally excited cyanoacetylene in the orion molecular cloud

Journal Article · Wed Sep 01 04:00:00 EDT 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/160242· OSTI ID:6718086

Goldsmith, P F; Snell, R L; Deguchi, S; Krotkov, R; Linke, R A

We have detected three rotational transitions from the ..nu../sub 7/ vibrationally excited state of cyanoacetylene in the Orion molecular cloud. This state lies approximately 320 K above the ground state. The width of these lines is 15 km s/sup -1/, and their central velocity is 5 km s/sup -1/. We suggest that the vibrationally excited lines are produced in the same region responsible for the prominent low velocity shoulder on the ground vibrational state HC/sub 3/N emission lines. We have mapped this ground-state feature using the 14 m FCRAO antenna and find the peak to be located at right ascension 5/sup h/32/sup m/47/sup s/.1 (1 sigma) and declination -5/sup 0/24'22'' +- 3'' (1 sigma), very near the infrared source IRc2. The emitting region was not resolved, but 2 sigma upper limits on the source size of 27'' in right ascension x 26'' in declination were obtained. We were unable to detect emission from the ..nu../sub 6/ or the 2..nu../sub 7/ states of HC/sub 3/N. The small source size and close proximity to the strong sources of infrared radiation present inthe KL region make infrared absorption an important mechanism in the excitation of the vibrational levels of cyanoacetylene. The results of statistical equilibrium and radiative transfer calculations indicate that infrared absorption provides a satisfactory explanation of our ..nu../sub 7/ HC/sub 3/N observations for IR source color temperatures >150 K and effective filling factors 0.2-0.5. The excitation of the high-J rotational lines of HC/sub 3/N is found to be predominantly due to collisions. We feel that the region responsible for the HC/sub 3/N vibrationally excited and high-J rotational emission is probably approx.6'' in diameter with n(H/sub 2/)approx.10/sup 7/ cm/sup -3/ and T/sub gas/ = 150-250 K. We also present upper limits for vibrationally excited cyanoacetylene emission in 10 other sources.

• Research Organization: Five College Radio Astronomy Observatory, University of Massachusetts, Amherst
• OSTI ID: 6718086
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 260:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
COLLISIONS
ELECTROMAGNETIC RADIATION
EMISSION SPECTRA
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
INFRARED RADIATION
INTERSTELLAR GRAINS
LINE WIDTHS
MOLECULE COLLISIONS
NEBULAE
NITRILES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PARTICLES
PROPIOLONITRILE
RADIATIONS
ROTATIONAL STATES
SPECTRA
VIBRATIONAL STATES