THE C(³P) + NH₃REACTION IN INTERSTELLAR CHEMISTRY. I. INVESTIGATION OF THE PRODUCT FORMATION CHANNELS

Abstract

The product formation channels of ground state carbon atoms, C( 3 P), reacting with ammonia, NH 3 , have been investigated using two complementary experiments and electronic structure calculations. Reaction products are detected in a gas flow tube experiment (330 K, 4 Torr) using tunable vacuum-ultraviolet (VUV) photoionization coupled with time of flight mass spectrometry. Temporal profiles of the species formed and photoionization spectra are used to identify primary products of the C + NH 3 reaction. In addition, H-atom formation is monitored by VUV laser induced fluorescence (LIF) from room temperature to 50 K in a supersonic gas flow generated by the Laval nozzle technique. Electronic structure calculations are performed to derive intermediates, transition states, and complexes formed along the reaction coordinate. The combination of photoionization and LIF experiments supported by theoretical calculations indicate that in the temperature and pressure range investigated, the H + H 2 CN production channel represents 100% of the product yield for this reaction. Kinetics measurements of the title reaction down to 50 K and the effect of the new rate constants on interstellar nitrogen hydride abundances using a model of dense interstellar clouds are reported in Paper II.

A combined theoretical and experimental investigation of the kinetics and dynamics of the O(1D) + D2reaction at low temperature

“…The experimental setup has been described in earlier papers, 76,77 while modifications that allowed the kinetics of atom-molecule reactions to be studied are described in more recent work. 16,70,71,75,[78][79][80][81][82][83][84][85][86] In an identical manner to previous investigations of excited state atom reactions, 16,70,71,75,78,81,[84][85][86] only Laval nozzles employing argon were used for these experiments as a result of the fast electronic quenching of O( 1 D) atoms by carrier gases such as N 2 . 75 These Ar based nozzles allowed uniform supersonic flows to be generated at specified temperatures of 50 K, 75 K and 127 K, with calculated densities in the range (1.26-2.59) Â 10 17 cm À3 and flow velocities between 419 and 505 m s À1 .…”

CRF-PEPICO: Double velocity map imaging photoelectron photoion coincidence spectroscopy for reaction kinetics studies

“…Photoionization mass spectrometry (PIMS) 1-4 is a universal, sensitive, selective, and multiplexed analytical technique to interrogate chemical reactions and has been very productive at tunable vacuum ultraviolet synchrotron light sources 5 in combustion studies, 6 among numerous other fields. 7 At the Chemical Dynamics Beamline of the Advanced Light Source, the time-resolved multiplexed photoionization mass spectrometer (MPIMS) 5 has detected and enabled the study of longsought reactive intermediates important in combustion 8,9 and atmospheric 10,11 chemistry, and has provided isomer-resolved product studies of chemistry relevant to astrochemical environments [12][13][14] including Titan, Saturn's largest moon. 15 More a) Authors to whom correspondence should be addressed: bsztaray@ pacific.edu and dlosbor@sandia.gov specifically, it enables the study of bimolecular chemical reactions by observing all reactants and products simultaneously, with enough dynamic range (10 5 ) to detect minor concentrations of key reactive intermediates in the presence of other species at much higher concentrations.…”

Sustained oscillations in interstellar chemistry models

“…In the HIP environment considered here, atomic carbon C (Bourgalais et al 2015;Hickson et al 2015) and ionized carbon C + are the main destruction agents (see Fig. 17) which finally lead to the formation of a CN bond within a large variety of species (HCN, HNC, HCNH + ,...), as displayed in Fig.…”