Doubly 15N-substituted diazenylium: THz laboratory spectra and fractionation models
Journal article, 2017

Context. Isotopic fractionation in dense molecular cores has been suggested as a possible origin of large 14N/15N ratio variations in solar system materials. While chemical models can explain some observed variations with different fractionation patterns for molecules with –NH or –CN functional groups, they fail to reproduce the observed ratios in diazenylium (N2H+). Aims. Observations of doubly 15N-substituted species could provide important constraints and insights for theoretical chemical models of isotopic fractionation. However, spectroscopic data are very scarce. Methods. The rotational spectra of the fully 15N-substituted isopologues of the diazenylium ion, 15N2H+ and 15N2D+, have been investigated in the laboratory well into the THz region by using a source-modulation microwave spectrometer equipped with a negative glow discharge cell. An extended chemical reaction network has been used to estimate what ranges of 15N fractionation in doubly 15N-substituted species could be expected in the interstellar medium (ISM). Results. For each isotopologue of the H- and D-containing pair, nine rotational transitions were accurately measured in the frequency region 88 GHz–1.2 THz. The analysis of the spectrum provided very precise rest frequencies at millimeter and sub-millimeter wavelengths, useful for the radioastronomical identification of the rotational lines of 15N2H+ and 15N2D+ in the ISM.





molecular data


L. Dore

University of Bologna

L. Bizzocchi

Max Planck Society

Eva Wirström

Astronomy and Plasmaphysics

C. Degli Esposti

University of Bologna

F. Tamassia

University of Bologna

S. B. Charnley

NASA Goddard Space Flight Center

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 604 A26- A26

Subject Categories

Analytical Chemistry

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics


Basic sciences



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4/4/2018 1