Collisional excitation of doubly deuterated ammonia ND$_\mathsf{2}$H by helium
نویسندگان
چکیده
منابع مشابه
Collisional excitation of doubly and triply deuterated ammonia ND 2 H and ND 3 by H 2 F . Daniel
The availability of collisional rate coefficients is a prerequisite for an accurate interpretation of astrophysical observations, since the observed media often harbour densities where molecules are populated under non-local thermodynamic equilibrium conditions. In the current study, we present calculations of rate coefficients suitable to describe the various spin isomers ofmultiply deuterated...
متن کاملInterstellar Triply Deuterated Ammonia
Research on interstellar ND3 is reviewed and updated from the discovery papers. Results from observations of a dozen sources at centimeter and submillimeter wavelengths are presented. The two data sets are consistent, but do not constrain the excitation conditions in the ND3emitting gas. The column density ratios of NH3/NH2D, NH2D/ND2H and ND3/ND2H, observed in similar sized beams, are ≈10, and...
متن کاملLetter to the Editor Detection of doubly deuterated ammonia in L134N
ND2H has been detected for the first time in the dense core of L134N, at the peak ammonia position. The abundance ratio [ND2H]/[NH2D] is 0.05, a slightly smaller value than the deuterium fractionation observed for ammonia [NH2D]/[NH3] ∼ 0.1 (Tiné et al. 2000). This is the second doubly deuterated species detected so far in the interstellar medium, and the first one in a cold dense core. The che...
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We present the first results from a time-dependent chemical model to include a gas-phase reaction scheme for producing doubly-deuterated species. Under normal conditions the formation of these species is inefficient. However, when the effects of the freeze out of gas phase species onto grains is included in the chemistry we find that the fractionation of both singly and doubly deuterated specie...
متن کاملCollisional excitation of hydrogen and the determination of the primordial helium abundance from H ii regions
This paper investigates the effect of collisional enhancement of the hydrogen lines on the derivation of the helium abundances in low metallicity H ii regions. For this, we have constructed a grid of photoionization models relevant for the analysis of giant H ii regions in blue compact galaxies. We show that the effect of collisional excitation on the Hα/Hβ ratio can be quite important (up to 8...
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ژورنال
عنوان ژورنال: Astronomy & Astrophysics
سال: 2007
ISSN: 0004-6361,1432-0746
DOI: 10.1051/0004-6361:20066267