Terahertz Spectroscopy of the Amidogen Radical, NH2

Müller, H. S. P.; Klein, H.; Белов, С. П.; Winnewisser, G.; Morino, Isamu; Yamada, Kōichi; Saito, Shuji

doi:10.1006/jmsp.1999.7820

Cited by 28 publications

(11 citation statements)

References 23 publications

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“…Figure 1 shows the detection of the hyperfine structure (HFS) of the N = 0 − 1, J = 1 2 − 3 2 , and J = 1 2 − 1 2 transitions of amidogen in its ortho form, with their strongest components at the rest frequencies 952.578354 GHz and 959.511716 GHz, respectively (Müller et al 1999). The HFS is almost entirely resolved with an intensity ratio that clearly deviates from optically thin LTE excitation.…”

Section: Resultsmentioning

confidence: 99%

“…(a) For NH, the quantum numbers for the rotational transition N J are F 1 = I H + J and F = I N + F 1 (Klaus et al 1997). For the N Ka Kc J rotational transition of NH 2 , the quantum numbers are F 1 = I N + J and F = I H + F 1 (Müller et al 1999). In the case of ammonia, quantum numbers are given separately for J = N + S and (K, ǫ), where ǫ is the symmetry index (see Maret et al 2009).…”

Section: Resultsmentioning

confidence: 99%

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Nitrogen hydrides in the cold envelope of IRAS 16293-2422

Hily-Blant

Maret

Bacmann

et al. 2010

A&A

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Nitrogen is the fifth most abundant element in the Universe, yet the gas-phase chemistry of N-bearing species remains poorly understood. Nitrogen hydrides are key molecules of nitrogen chemistry. Their abundance ratios place strong constraints on the production pathways and reaction rates of nitrogen-bearing molecules. We observed the class 0 protostar IRAS 16293-2422 with the heterodyne instrument HIFI, covering most of the frequency range from 0.48 to 1.78 THz at high spectral resolution. The hyperfine structure of the amidogen radical o-NH 2 is resolved and seen in absorption against the continuum of the protostar. Several transitions of ammonia from 1.2 to 1.8 THz are also seen in absorption. These lines trace the low-density envelope of the protostar. Column densities and abundances are estimated for each hydride. We find that NH:NH 2 :NH 3 ≈ 5:1:300. Dark clouds chemical models predict steady-state abundances of NH 2 and NH 3 in reasonable agreement with the present observations, whilst that of NH is underpredicted by more than one order of magnitude, even using updated kinetic rates. Additional modelling of the nitrogen gas-phase chemistry in dark-cloud conditions is necessary before having recourse to heterogen processes.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Nitrogen hydrides in the cold envelope of IRAS 16293-2422

Hily-Blant

Maret

Bacmann

et al. 2010

A&A

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“…Wavenumbers of transitions in the 3 μm region (both ν 1 -and ν 3 -bands) are taken from McKellar et al (1990) while wavenumbers of the transitions betweenÃ(1,v 2 ',0) and X(0,0,0) orX(1,0,0) are taken from Dressler & Ramsay (1959) and Ross et al (1988). Einstein A coefficients are calculated on the basis of the molecular constants (Müller et al 1999;Burkholder et al 1988;McKellar et al 1990) and ab initio calculations of transition moments for vibronic transitions by Jensen et al (2003). Table 5 lists the g-factors of NH 2 at 1 AU from the Sun (the relative velocity to the Sun is assumed to be zero) for various rotational temperatures.…”

Section: Tablementioning

confidence: 99%

FLUORESCENCE EXCITATION MODELS OF AMMONIA AND AMIDOGEN RADICAL (NH₂) IN COMETS: APPLICATION TO COMET C/2004 Q2 (MACHHOLZ)

Kawakita

Mumma

2011

ApJ

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Ammonia is a major reservoir of nitrogen atoms in cometary materials. However, detections of ammonia in comets are rare, with several achieved at radio wavelengths. A few more detections were obtained through near-infrared observations (around the 3 μm wavelength region), but moderate relative velocity shifts are required to separate emission lines of cometary ammonia from telluric absorption lines in the 3 μm wavelength region. On the other hand, the amidogen radical (NH 2 -a photodissociation product of ammonia in the coma) also shows rovibrational emission lines in the 3 μm wavelength region. Thus, gas production rates for ammonia can be determined from the rovibrational emission lines of ammonia (directly) and amidogen radical (indirectly) simultaneously in the near-infrared. In this article, we present new fluorescence excitation models for cometary ammonia and amidogen radical in the near-infrared, and we apply these models to the near-infrared high-dispersion spectra of comet C/2004 Q2 (Machholz) to determine the mixing ratio of ammonia to water in the comet. Based on direct detection of NH 3 lines, the mixing ratio of NH 3 /H 2 O is 0.46% ± 0.03% in C/2004 Q2 (Machholz), in agreement with other results. The mixing ratio of ammonia determined from the NH 2 observations (0.31%-0.79%) is consistent but has relatively larger error, owing to uncertainty in the photodissociation rates of ammonia. At the present level of accuracy, we confirm that NH 3 could be the sole parent of NH 2 in this comet.

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“…Previous attempts to determine the off-diagonal dipole-dipole term T ab in the spectra of NH 2 [46,47], PH 2 [51], and AsH 2 [52,53] did not succeed, despite accessing the nearly degenerate ortho/ para pair of levels N 0N and N 1N . NF 2 was considered a better candidate molecule for such a determination because of the large magnetic moment of the 19 F nucleus and the fact that the rotational levels are closer together than in a dihydride.…”

Section: Hyperfine Parametersmentioning

confidence: 91%

“…and NH 2 in their 2 B 1 ground states Values determined by Müller et al[46], Gendriesch et al[47]. c Value determined indirectly from a study of NHD by Steimle et al[48] from the isotopic shifts of the T ii tensor.…”

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confidence: 98%