The far-infrared laser magnetic resonance spectrum of the 13CH radical

Davidson, Stephen A; Evenson, K. M.; Brown, John M.

doi:10.1016/j.jms.2003.09.002

Cited by 15 publications

(15 citation statements)

References 36 publications

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“…For CH, this data set (see table 2 of ref. 12) includes earlier measurements from astronomical observations (6), MODR (14,15), tunable FIR (12), microwave (16), and submillimeter-wave (13) spectroscopy; for 13 CH, the data include frequencies from MODR (17,18) and laser magnetic resonance (19). Details of the Hamiltonian are given in ref.…”

Section: As the Rotational Energy Level Diagram Inmentioning

confidence: 99%

“…13) have been obtained, as well as microwave-optical double resonance (MODR) measurements (14,15) and a few centimeter-wave measurements at fairly high J ϳ 6.5 (16) to better pin down the lambda-doubling intervals. 13 CH has been studied by some of the same techniques (17)(18)(19), but owing to the lack of tunable FIR measurements, its rotational spectrum until now could only be predicted to a few megahertz.…”

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confidence: 99%

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Detection of low-frequency lambda-doublet transitions of the free ¹² CH and ¹³ CH radicals

McCarthy

Mohamed

Brown

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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By Fourier transform microwave spectroscopy, lambda-doubling transitions of 12 CH and 13 CH in the lowest rotational levels of the X 2 ͟1/2 ground state have been directly detected, which has not been done previously. For both radicals, hyperfine-split lines have been measured to an accuracy of better than 1 ppm between 3 and 15 GHz, an improvement of at least 2 orders of magnitude over previous laboratory data. The measured frequencies have been combined with all previous data for CH and 13 CH in the v ‫؍‬ 0 level of the X 2 ͟ electronic state to determine improved hyperfine parameters. The production of CH from various gases also has been studied and, with methanol, the yield of CH relative to OH. Astronomical studies of CH in higher rotational levels and 13 CH can now be undertaken on the basis of the present work.microwave spectroscopy ͉ molecular data ͉ radio astronomy T he CH radical is widely distributed in astronomical sources, observed in planetary atmospheres, comets, HI and HII regions, dark molecular clouds, and planetary nebulae. It was one of the first interstellar molecules identified (1, 2), by means of detection in the optical band of a single line [R 2 (1)] near 4,300 Å of the A 2 ⌬ 3 X 2 ͟ electronic transition. It has now been observed in other parts of the spectrum as follows: (i) in the radio, by detection of lambda-doubling transitions near 3.3 GHz (3-5) in the lowest rotational level (J ϭ 1͞2) of the X 2 ͟ 1/2 state; (ii) near 700 MHz (6) in the lowest rotational level of the upper fine structure ladder (X 2 ͟ 3/2 ); (iii) in the far-infrared (FIR), by detection in both absorption (7) and emission (8) of its fundamental rotational transitions at 149.09 and 149.39 m; and (iv) in the far UV, including the diffuse feature at 1369.13 Å (9). There is little astronomical data on the rare isotopic species 13 CH, but some of its lines have been identified in the solar spectrum (10).Because of the astronomical importance of CH, considerable effort has been devoted in the laboratory to measure its rotational spectrum. Early studies by laser magnetic resonance (ref.11 and references therein) allowed some of the more interesting lines to be predicted to an uncertainty of Ϸ2 MHz. Since then, more accurate FIR spectra (good to 100 kHz; ref. 12) and submillimeter-wave spectra (good to 30-100 kHz; ref. 13) have been obtained, as well as microwave-optical double resonance (MODR) measurements (14, 15) and a few centimeter-wave measurements at fairly high J ϳ 6.5 (16) to better pin down the lambda-doubling intervals. 13 CH has been studied by some of the same techniques (17-19), but owing to the lack of tunable FIR measurements, its rotational spectrum until now could only be predicted to a few megahertz.Although much laboratory spectroscopy has already been done on CH and 13 CH, still more is needed: many of the lambda-doubling transitions have not been measured to high precision, and only a small number of the FIR spin-rotational intervals have been detected at adequately high signal-to-noise. It is parti...

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Section: As the Rotational Energy Level Diagram Inmentioning

confidence: 99%

mentioning

confidence: 99%

Detection of low-frequency lambda-doublet transitions of the free ¹² CH and ¹³ CH radicals

McCarthy

Mohamed

Brown

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…One way to check the opacity of Sgr B2 is to use the less abundant 13 CH isotopomer whose 2 Π 1/2 J = 3/2-1/2 transition has components at 149.79 µm and 150.09 µm (Davidson et al 2004). Langer & Penzias (1990) find a 12 C/ 13 C ratio towards Sgr B2 of 24 ± 1 using observations of 12 C 18 O and 13 C 18 O.…”

Section: Chmentioning

confidence: 99%

Far-infrared detection of methylene

Polehampton¹,

Menten²,

Brünken

et al. 2005

A&A

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Abstract. We present a clear detection of CH 2 in absorption towards the molecular cloud complexes Sagittarius B2 and W49 N using the ISO Long Wavelength Spectrometer. These observations represent the first detection of its low excitation rotational lines in the interstellar medium. Towards Sagittarius B2, we detect both ortho and para transitions allowing a determination of the total CH 2 column density of N(CH 2 ) = (7.5± 1.1)× 10 14 cm −2 . We compare this with the related molecule, CH, to determine [CH/CH 2 ] = 2.7±0.5. Comparison with chemical models shows that the CH abundance along the line of sight is consistent with diffuse cloud conditions and that the high [CH/CH 2 ] ratio can be explained by including the effect of grain-surface reactions.

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“…The effective Hamiltonian was cast in the N 2 form as described by Brown et al [30] with the Zeeman terms as described in [31]. This is the same Hamiltonian as that used to analyse the far-infrared LMR spectra of 12 CH in v = 0 [11], 13 CH [15] and CD [17]. The eigenstates were identified in terms of Hund's case (b) quantum numbers.…”

Section: Least-squares Fitmentioning

confidence: 99%

“…In addition to the dominant isotopomer 12 CH, two others, 13 CH [14][15][16] and CD [17], have also been thoroughly studied at very high resolution. Less information is available on the radical in vibrationally excited levels.…”

Section: Introductionmentioning

confidence: 99%

The far-infrared and microwave spectra of the CH radical in the v=1 level of the X2Π state

Jackson

Zink

McCarthy

et al. 2008

Journal of Molecular Spectroscopy

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The far-infrared laser magnetic resonance spectrum of the 13CH radical

Cited by 15 publications

References 36 publications

Detection of low-frequency lambda-doublet transitions of the free ¹² CH and ¹³ CH radicals

Detection of low-frequency lambda-doublet transitions of the free ¹² CH and ¹³ CH radicals

Far-infrared detection of methylene

The far-infrared and microwave spectra of the CH radical in the v=1 level of the X2Π state

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The far-infrared laser magnetic resonance spectrum of the 13CH radical

Cited by 15 publications

References 36 publications

Detection of low-frequency lambda-doublet transitions of the free 12 CH and 13 CH radicals

Detection of low-frequency lambda-doublet transitions of the free 12 CH and 13 CH radicals

Far-infrared detection of methylene

The far-infrared and microwave spectra of the CH radical in the v=1 level of the X2Π state

Contact Info

Product

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Detection of low-frequency lambda-doublet transitions of the free ¹² CH and ¹³ CH radicals

Detection of low-frequency lambda-doublet transitions of the free ¹² CH and ¹³ CH radicals