Isotopic Fractionation of Nitrogen in Ammonia in the Troposphere of Jupiter

Liang, Mao‐Chang; Cheng, Bing‐Ming; Lu, Hsiao Chi; Chen, Hong Kai; Alam, Mohammed S.; Lee, Yuan‐Pern; Yung, Yuk L.

doi:10.1086/513192

Cited by 17 publications

(8 citation statements)

References 39 publications

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“…For the photodissociation efficiency with respect to the solar radiation it would be necessary to conduct complementary laboratory experiments for measuring the absorption cross section for both 14 NH 3 and 15 NH 3 . Some results of laboratory experiments relative to this problem have, nevertheless, already been published (Suto & Lee 1983;Liang et al 2007). These papers show that the oscillator strength f, defined by 1.13 × 10 −6 σ dν (where σ is the absorption cross section in megabarns (= 10 −18 cm 2 ) and ν the wavenumber (cm −1 )) is only 7.3% greater for 15 NH 3 compared to 14 NH 3 (Liang et al 2007) in the 165-220 nm range (corresponding to the main region of photodissociation for these molecules).…”

Section: Discussionmentioning

confidence: 99%

“…Some results of laboratory experiments relative to this problem have, nevertheless, already been published (Suto & Lee 1983;Liang et al 2007). These papers show that the oscillator strength f, defined by 1.13 × 10 −6 σ dν (where σ is the absorption cross section in megabarns (= 10 −18 cm 2 ) and ν the wavenumber (cm −1 )) is only 7.3% greater for 15 NH 3 compared to 14 NH 3 (Liang et al 2007) in the 165-220 nm range (corresponding to the main region of photodissociation for these molecules). For shorter wavelengths, especially the Lyα region, only 14 NH 3 absorption cross sections are available (Suto & Lee 1983).…”

Section: Discussionmentioning

confidence: 99%

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Toward a Unique Nitrogen Isotopic Ratio in Cometary Ices

Rousselot

Pirali

Jehin

et al. 2013

ApJ

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Determination of the nitrogen isotopic ratios in different bodies of the solar system provides important information regarding the solar system's origin. We unambiguously identified emission lines in comets due to the 15 NH 2 radical produced by the photodissociation of 15 NH 3 . Analysis of our data has permitted us to measure the 14 N/ 15 N isotopic ratio in comets for a molecule carrying the amine (-NH) functional group. This ratio, within the error, appears similar to that measured in comets in the HCN molecule and the CN radical, and lower than the protosolar value, suggesting that N 2 and NH 3 result from the separation of nitrogen into two distinct reservoirs in the solar nebula. This ratio also appears similar to that measured in Titan's atmospheric N 2 , supporting the hypothesis that, if the latter is representative of its primordial value in NH 3 , these bodies were assembled from building blocks sharing a common formation location.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Toward a Unique Nitrogen Isotopic Ratio in Cometary Ices

Rousselot

Pirali

Jehin

et al. 2013

ApJ

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“…The results of two high-resolution optical experiments (Wu et al 2007;Liang et al 2007) were supplemented by an electron energy-loss measurement (Samson et al 1987) over the wavelength ranges listed in Table 12 to determine a best photoabsorption cross section for NH 3 . Since the cross section is broad and continuous, 100% dissociation efficiency is assumed below the ionisation threshold.…”

Section: Nh 3 -Ammoniamentioning

confidence: 99%

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

425

442

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A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic physical processes involved. These have been used to calculate dissociation and ionisation rates, with uncertainties, in a standard ultraviolet interstellar radiation field (ISRF) and for other wavelength-dependent radiation fields, including cool stellar and solar radiation, Lyman-α dominated radiation, and a cosmic-ray induced ultraviolet flux. The new ISRF rates generally agree within 30% with our previous compilations, with a few notable exceptions. Comparison with other databases such as PHIDRATES is made. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic C, and self-shielding column densities. The relative importance of these shielding types depends on the atom or molecule in question and the assumed dust optical properties. All of the new data are publicly available from the Leiden photodissociation and ionisation database. Sensitivity of the calculated rates to variation of temperature and isotope, and uncertainties in measured or calculated cross sections, are tested and discussed. Tests were conducted on the new rates with an interstellar-cloud chemical model, and find general agreement (within a factor of two) in abundances obtained with the previous iteration of the Leiden database assuming an ISRF, and order-of-magnitude variations assuming various kinds of stellar radiation. The newly parameterised dust-shielding factors makes a factor-of-two difference to many atomic and molecular abundances relative to parameters currently in the UDfA and KIDA astrochemical reaction databases. The newly-calculated cosmic-ray induced photodissociation and ionisation rates differ from current standard values up to a factor of 5. Under high temperature and cosmic-ray-flux conditions the new rates alter the equilibrium abundances of abundant dark cloud abundances by up to a factor of two. The partial cross sections for H 2 O and NH 3 photodissociation forming OH, O, NH 2 and NH are also evaluated and lead to radiation-field-dependent branching ratios.

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“…To assess the abundances and photochemically induced changes in space, one must have quantitative information about the absorption cross sections of interstellar molecules in the VUV range (Miller & Yung 2000). For this purpose, we determined the absorption cross sections of several interstellar molecular species in the VUV range (Cheng et al 1999(Cheng et al , 2002(Cheng et al , 2004(Cheng et al , 2006Bahou et al 2001;Lee et al 2001;Liang et al 2007), but most such measurements were made near 300 K.…”

Section: Introductionmentioning

confidence: 99%

ABSORPTION CROSS SECTION OF GASEOUS ACETYLENE AT 85 K IN THE WAVELENGTH RANGE 110-155 nm

Cheng¹,

Chen²,

Lu³

et al. 2011

ApJS

Self Cite

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Absorption spectra and absorption cross sections of gaseous acetylene, C 2 H 2 , at 298 and 85 K were measured in the wavelength range 110-155 nm with a slit-jet system coupled to a synchrotron as a source of vacuum ultraviolet light. Using published spectral parameters of C 2 H 2 , we simulated the absorption profile for the Rydberg transition to state 4R 0 in the range 124.6-125.1 nm, according to which the temperature of the jet-expanded sample at stagnation pressure 200 Torr is 85 ± 5 K. Our cross sections of C 2 H 2 are applicable for determining properties sensitive to temperature for diagnostic work on Saturn and Titan.

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Isotopic Fractionation of Nitrogen in Ammonia in the Troposphere of Jupiter

Cited by 17 publications

References 39 publications

Toward a Unique Nitrogen Isotopic Ratio in Cometary Ices

Toward a Unique Nitrogen Isotopic Ratio in Cometary Ices

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

ABSORPTION CROSS SECTION OF GASEOUS ACETYLENE AT 85 K IN THE WAVELENGTH RANGE 110-155 nm

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