title: Detection of nitrogen-protonated nitrous oxide (HNNO+) by rotational spectroscopy.
abstract: The rotational spectrum of nitrogen-protonated nitrous oxide (HNNO(+)), an isomer whose existence was first inferred from kinetic studies more than 30 years ago, has now been detected by Fourier transform microwave spectroscopy, guided by new high-level coupled-cluster calculations of its molecular structure. From high-resolution measurements of the hyperfine splitting in its fundamental rotational transition, the rotational constant (B + C)/2 and the quadrupole tensor element χaa(N) for both nitrogen atoms have been precisely determined. The derived constants agree well with quantum-chemical calculations here and others in the literature. The χaa(N) values for the two isomers of protonated nitrous oxide are qualitatively consistent with the valence bond description of H-N═N(+)═O for the electronic structure of the nitrogen-protonated form and N≡N(+)-O-H for the oxygen-protonated form. HNNO(+) is found to be 2-4 times less abundant than NNOH(+) under a range of experimental conditions, as might be expected because this metastable isomer is known to be only ∼6 kcal mol(-1) less stable than ground-state NNOH(+) from kinetic measurements by Ferguson and co-workers.
authors.affiliation: Harvard-Smithsonian Center for Astrophysics , 60 Garden Street, Cambridge, Massachusetts 02138, United States.
authors.forename: Michael C
authors.initials: MC
authors.lastname: McCarthy
authors.forename: Oscar
authors.initials: O
authors.lastname: Martinez
authors.forename: Kyle N
authors.initials: KN
authors.lastname: Crabtree
authors.forename: Valerio
authors.initials: V
authors.lastname: Lattanzi
authors.forename: Stewart E
authors.initials: SE
authors.lastname: Novick
authors.forename: Sven
authors.initials: S
authors.lastname: Thorwirth