Detection of the N = 1 - 0 transition of C4H

Laser-induced fluorescence spectroscopy of the C4H and C4D radicals in a supersonic jet

“…We assigned the vibronic bands observed at 24 048 cm Ϫ1 ͓C͔ and 24 491 cm Ϫ1 ͓J͔ to 5 ( 2 ⌺ ϩ ) and 3 5 ( 2 ⌺ ϩ ) of the 5 quite irregular. In fact, the fundamental band, 5 ( 2 ⌺ ϩ ), is very close to the origin band; they are separated by only 14.2 cm Ϫ1 , this value being much smaller than the lowest bending frequency.…”

“…As described in the previous section, the molecular constants for most of the observed vibronic bands were determined, and assigned to two vibrational progressions, 5 ͑with a large Renner-Teller interaction͒ and 6 ͑with a small Renner-Teller interaction͒. The vibronic structure in the B 2 ⌸ i state should be analyzed by considering the vibronic interaction and the spin-orbit interaction together.…”

“…[42][43][44][45][46] We analyzed the vibronic bands under the following assumptions for simplification: ͑1͒ only the R-T interaction was taken into account explicitly, and H-T ͑first order͒ and other higher order interactions including the intermode coupling 47,48 were ignored, ͑2͒ contributions from the 7 bending mode were neglected, since no band involving the 7 mode was observed, and ͑3͒ in deriving the true spinorbit interaction constant, A SO , which does not contain contributions from the vibronic coupling, we considered only the 5 …”

“…The linear carbon chain molecule C 4 H ͑CCCCH͒ is a member of the C n H series of molecules which are important as intermediate species in interstellar chemistry [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] and in combustion chemistry, where larger carbon clusters such as C 60 are observed to be produced. It was first identified in the envelope of the carbon star, IRCϩ10216 in 1978 by radioastronomy, 8 and its discovery was one of the first spectroscopic identifications of long carbon chain free radicals containing four or more atoms in the gas phase.…”

“…Since then, C n H (nϭ3 -9,11), [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] C n N (nϭ3,5), 18,19 and C n S (n ϭ3 -5) [20][21][22][23] have been identified in the interstellar medium or in laboratory experiments. Among these carbon-chain free radicals, C 4 H has been extensively studied in the microwave region as one of the most important species for probing interstellar conditions; it has been detected in many important astronomical sources: in a diffuse gas of the Orion arm, 3 in the dark molecular cloud TMCϪ1, [4][5][6][7] and also in the carbonrich circumstellar envelope of IRCϩ10216. [8][9][10][11] The first laboratory detection of C 4 H was reported by Gottlieb et al in 1983 by microwave spectroscopy in a discharge flow system through C 2 H 2 in Ar, 24 five years after the first astronomical identification.…”