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Title: A LABORATORY STUDY OF C{sub 3}H{sup +} AND THE C{sub 3}H RADICAL IN THREE NEW VIBRATIONALLY EXCITED {sup 2}Σ STATES USING A PIN-HOLE NOZZLE DISCHARGE SOURCE

Rotational lines of the positive molecular ion C{sub 3}H{sup +} and of the neutral C{sub 3}H radical in three new vibrationally excited states with {sup 2}Σ symmetry have been detected in a supersonic molecular beam in the centimeter-wave band. The fundamental rotational line of the ion is quite weak, but is observed with similar intensity in a dc discharge through several different hydrocarbon gases when helium is the buffer gas. Under these conditions, the fractional abundance of C{sub 3}H{sup +} relative to C{sub 3}H is estimated to be of order 10{sup −4}, i.e., toward the lower end of the ratio (10{sup −3}–10{sup −4}) found for protonated ions using the same discharge nozzle. For each new {sup 2}Σ state of the C{sub 3}H radical, spectroscopic constants, including those describing hydrogen hyperfine structure, have been determined to high precision. Lines of one {sup 2}Σ state (B = 11271 MHz) are particularly intense in our molecular beam; for this state and a second one (B = 11306 MHz), millimeter-wave transitions have also been observed between 180 and 340 GHz using a long path dc glow absorption spectrometer. On the basis of intensity measurements with this spectrometer, the inferred rotation–vibration constant α, and theoreticalmore » calculations, the state with B = 11271 MHz is tentatively assigned to the ν{sub 5} bending mode, predicted to lie ∼300 cm{sup −1} above ground.« less
Authors:
; ; ; ;  [1] ;  [2]
  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  2. National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States)
Publication Date:
OSTI Identifier:
22520076
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 217; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ABSORPTION SPECTROSCOPY; EXCITED STATES; GHZ RANGE; HOLES; HYDROCARBONS; HYDROGEN; HYPERFINE STRUCTURE; MHZ RANGE; MOLECULAR BEAMS; MOLECULAR IONS; MOLECULES; RADICALS; ROTATIONAL STATES