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J/ApJ/716/1315     Hyperfine levels of N2H+                    (Keto+, 2010)

Modeling molecular hyperfine line emission. Keto E., Rybicki G. <Astrophys. J., 716, 1315-1322 (2010)> =2010ApJ...716.1315K
ADC_Keywords: Atomic physics Keywords: ISM: molecules - radiative transfer Abstract: In this paper, we discuss two approximate methods previously suggested for modeling hyperfine spectral line emission for molecules whose collisional transition rates between hyperfine levels are unknown. Hyperfine structure is seen in the rotational spectra of many commonly observed molecules such as HCN, HNC, NH3, N2H+, and C17O. The intensities of these spectral lines can be modeled by numerical techniques such as Λ-iteration that alternately solve the equations of statistical equilibrium and the equation of radiative transfer. However, these calculations require knowledge of both the radiative and collisional rates for all transitions. For most commonly observed radio frequency spectral lines, only the net collisional rates between rotational levels are known. For such cases, two approximate methods have been suggested. The first method, hyperfine statistical equilibrium, distributes the hyperfine level populations according to their statistical weight, but allows the population of the rotational states to depart from local thermal equilibrium (LTE). The second method, the proportional method, approximates the collision rates between the hyperfine levels as fractions of the net rotational rates apportioned according to the statistical degeneracy of the final hyperfine levels. The second method is able to model non-LTE hyperfine emission. We compare simulations of N2H+ hyperfine lines made with approximate and more exact rates and find that satisfactory results are obtained. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 22 64 N2H+ hyperfine levels table3.dat 45 280 N2H+ hyperfine level data
See also: J/A+A/413/1177 : Spectroscopy of N2D+ hyperfine structure (Dore+, 2004) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Level [1/64] Level index 5- 11 F7.4 cm-1 E Energy of level 13- 16 F4.1 --- g Statistical weight 18 I1 --- J [0/7] J rotational quantum number 20 I1 --- F1 [0/8] F1 hyperfine quantum number 22 I1 --- F [0/9] F hyperfine quantum number
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Trans [1/280] Transition index 5- 6 I2 --- Up [4/64] Upper state (index from table2) 8- 9 I2 --- Low [1/55] Lower state (index from table2) 11- 20 E10.4 s-1 A Einstein A coefficient 22- 32 F11.7 GHz Freq [93.1716/652.099] Frequency 34- 45 A12 --- RInt Relative intensity
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 01-Jun-2012
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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