Microwave spectrum of the hydroxyl radical in the ν= 1 2Π32 state

Destombes, J. L.; Lemoine, B.; Marlière-Demuynck, C.

doi:10.1016/0009-2614(79)80619-3

Cited by 32 publications

(31 citation statements)

References 15 publications

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“…For OH, we included the lowest 10 rotational levels. The energy levels and Einstein A values were taken from O †er & van Dishoeck (1992) and Destombes et al (1977), respectively. When the temperature is high, the impact H 2 quenching rate coefficients are not sensitive to the temperature (Dewangan, Flower, & Alexander 1987 ;O †er & van Dishoeck 1992).…”

Section: Emission-line Intensitiesmentioning

confidence: 99%

Theoretical Modeling ofISOResults on Planetary Nebula NGC 7027

Yan

Federman

Dalgarno

et al. 1999

ApJ

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We present a thermal and chemical model of the neutral envelope of planetary nebula NGC 7027. In our model, the neutral envelope is composed of a thin dense shell of constant density and an outer stellar wind region with the usual inverse-square law density proÐle. The thermal and chemical structure is calculated with the assumption that the incident radiation Ðeld on the inner surface equals 0.5 ] 105 times DraineÏs Ðt to the average interstellar far-ultraviolet Ðeld. The rate coefficient for formation on H 2 grains is assumed to be the usual value to take into account the lower dust-gas mass ratio in the 1 5 neutral envelope of NGC 7027. The calculated temperature in the dense shell decreases from 3000 to under 200 K. Once the temperature drops to 200 K, we assume that it remains at 200 K until the outer edge of the dense shell is reached, so that the observed intensities of CO J \ 16È15, 15È14, and 14È13 lines can be reproduced. The 200 K temperature can be interpreted as the average temperature of the shocked gas just behind the forward shock front in the framework of the interacting stellar wind theory. We calculate the intensities of the molecular far-infrared rotational lines by using a revised version of the escape probability formalism. The theoretical intensities for rotational lines of CO (from J \ 29È28 to J \ 14È13), CH`, OH, and CH are shown to be in good agreement with ISO observations. The H 2 rovibrational line intensities are also calculated and are in agreement with available observations.

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Section: Emission-line Intensitiesmentioning

confidence: 99%

Theoretical Modeling ofISOResults on Planetary Nebula NGC 7027

Yan

Federman

Dalgarno

et al. 1999

ApJ

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“…Only the OH lines located in the centre and the southern edge of the disk are superposed on the observed continuum emission. peak flux of the observed OH line emission (for the OH transitions see: Destombes et al 1977). Nevertheless, in both cases the low pump efficiency indicates an unsaturated maser process.…”

Section: Understanding the Hydroxyl Emissionmentioning

confidence: 99%

“…Since the excitation mechanism of the OH molecules is most likely radiative pumping, the integrated infrared emission field determines the OH main-line ratio. Assuming a spectral-temperature of a single black-body or a single grey-body, the population in the OH ground level ( 2 Π 3/2 ) follows from the population cascade of the rotational and vibrational levels (Destombes et al 1977). By solving the rate equations for the individual levels up to J = 9/2, a gray-body temperature of 63 K and a black-body temperature of 68 K suggest a main-line ratio ranging from 1.98 or 3.00, respectively (note that for the gray body estimate additional infrared data has been used from Klaas et al 2001).…”

Section: Understanding the Hydroxyl Emissionmentioning

confidence: 99%

An embedded circumnuclear disk in Mrk 273

Klöckner

Baan

2004

A&A

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Abstract. Radio observations using very long baseline interferometry (VLBI) and the Westerbork interferometer have been carried out to study the hydroxyl Megamaser emission in Mrk 273 at different spatial resolutions. Line and continuum observations were carried out by the European VLBI network (EVN) at 1.6 GHz and display a number of distinct structural components in the central arcsec 2 region. The observed continuum emission shows three prominent regions with both flat and steep spectral indexes. The hydroxyl (OH) emission detected by the EVN measurements accounts for only 12 percent of the total OH emission in Mrk 273, but it does show the same dominant 1667 MHz line emission components as the WSRT observations. The spatial distribution of the maser emission provides a high resolution view of the molecular environment in the nuclear region. The OH emission has only been detected toward a distinct radio source in the northern nucleus with a spatial extent of 108 pc. The OH emission is only partially superposed on the radio continuum and is associated with the near-infrared emission source. The low pump efficiency of the maser and the OH main-line ratio suggest that this emission originates in an optically thin and unsaturated maser environment with a complex pumping scheme that cannot be explained by radiative infrared pumping with a single dust temperature. The specific line emission pattern and the line-of-sight velocities indicate the organized structure of an edge-on disk/TORUS with a Keplerian rotation surrounding a central object with a binding mass of 1.39 ± 0.16 × 10 9 M .

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“…transitions of the 2 n 3 / 2 , J = 15/2 state, have been measured previously (18) as shown in the third column of the table. Our measurements of these two .9. to result from an increase of the H 2 concentration in the supply gas since the recombination rate for the H atoms would then be larger.…”

Section: So Measurementsmentioning

confidence: 99%

Microwave spectrometer for the detection of transient gaseous species

Kolbe

Zollner

Leskovar

1981

Review of Scientific Instruments

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A microwave spectrometer and associated apparatus for the detection of unstable free radical species is described. The spectrometer, which operates over a frequency range from 66 to 73 GHz, consists of a tunable Fabry-Perot resonator followed by superhetrodyne detection for high sensitivity at low power levels. The resonator tuning is accomplished by means of a computer controlled stepping motor and by a piezoelectric transducer which also permits the use of source modulation and phase sensitive detection at 100 Hz. The sensitivity of the spectrometer is adequate to permit the detection of rotational transitions with absorption coefficients as small as 2 x 10" cm" .The operation of the spectrometer is demonstrated by the detection of the two free radical species OH and SO. In the case of OH, a number of A-doubling transitions, previously unobserved, are reported. K__ IntrMuctlon,Free radical products and intermediaries have been extensively studied (1-4) in gas-phase reactions induced photochemically, thermally in flames, and by direct admixture of active species such as H and 0 atoms. In such studies it is important to determine the concentrations of the free radical species as a function of time after the initiation of the reaction. In

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Microwave spectrum of the hydroxyl radical in the ν= 1 2Π32 state

Cited by 32 publications

References 15 publications

Theoretical Modeling ofISOResults on Planetary Nebula NGC 7027

Theoretical Modeling ofISOResults on Planetary Nebula NGC 7027

An embedded circumnuclear disk in Mrk 273

Microwave spectrometer for the detection of transient gaseous species

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