Ammonium salts are a reservoir of nitrogen on a cometary nucleus and possibly on some asteroids.

The measured nitrogen-to-carbon ratio in comets is lower than for the Sun, a discrepancy which could be alleviated if there is an unknown reservoir of nitrogen in comets. The nucleus of comet 67P/Churyumov-Gerasimenko exhibits an unidentified broad spectral reflectance feature around 3.2 micrometers, which is ubiquitous across its surface.

Electronic spectrum of the protonated diacetylene cation (HCH).

The B̃A←X̃A electronic band system of the protonated diacetylene cation (HCH) is measured over the 230-295 nm range by photodissociating HCH ions stored in a cryogenic ion trap and by photodissociating HCH tagged with Ar and N in a tandem mass spectrometer. The B̃A←X̃A band system has an origin at 34 941 cm for HCH, 34 934 cm for HCH-Ar, and 34 920 cm for HCH-N. The spectra of HCH, HCH-Ar, and HCH-N display similar vibronic structure, which is assigned using ab initio calculations to progressions in two symmetric a C-C stretch vibrational modes (ν and ν), with band spacings of 860 and 1481 cm, respectively.

Twisted Intramolecular Charge Transfer in Protonated Amino Pyridine.

The excited state properties of protonated ortho (2-), meta (3-), and para (4-) aminopyridine molecules have been investigated through UV photofragmentation spectroscopy and excited state coupled-cluster CC2 calculations. Cryogenic ion spectroscopy allows recording well-resolved vibronic spectroscopy that can be reproduced through Franck-Condon simulations of the ππ* local minimum of the excited state potential energy surface. The excited state lifetimes have also been measured through a pump-probe excitation scheme and compared to the estimated radiative lifetimes.

Diffusion of molecules in the bulk of a low density amorphous ice from molecular dynamics simulations.

The diffusion of molecules in interstellar ice is a fundamental phenomenon to take into account while studying the formation of complex molecules in this ice. This work presents a theoretical study on the diffusion of H2O, NH3, CO2, CO, and H2CO in the bulk of a low density amorphous (LDA) ice, while taking into account the physical conditions prevailing in space, i.e.