15117-75-6Relevant academic research and scientific papers
Examination of the product channels in the reactions of NH(a 1Δ) with H2 and D2
Tezaki, Atsumu,Okada, Satoru,Matsui, Hiroyuki
, p. 3876 - 3883 (1993)
A flash photolysis study (193 nm) of HNCO has been conducted and the mechanisms of the reactions NH(a 1Δ) + H2 -> NH2 + H (1) and NH(a 1Δ) + D2 -> products (2) have been examined in detail at 295 +/- 3 K by monitoring NH(a 1Δ), H, D, NH2, and their D substituents via the laser induced fluorescence technique.From the pseudo-first-order analysis of the decay rate for NH(a 1Δ), rate constants have been determined as k1 = (3.96 +/- 0.17) x 10-12 and k2 = (2.62 +/- 0.08) x 10-12. (All the rate constants are expressed in units of cm3 molecule-1 s-1.) These rate constants are consistent with those determined from the time dependence of H and D atoms: they are k1 = (3.76 +/- 0.70) x 10-12 and k2 = (2.78 +/- 0.17) x 10-12.No pressure dependence has been observed for 10-100 Torr He.The branching fraction for H and D atoms as products for reaction (2) has been found to be / = 0.24/0.76, where D production is more abundant than statistically predicted.This indicates that reaction (2) is dominated by insertion of NH(a 1Δ) into the D2 bond, but vibrational energy of the reaction intermediate NHD2 is still localized in newly formed N-D bonds before it passes through the exit barrier into NHD + D or ND2 + H channels.NH2(X 2B1) was observed in (0,0,0) and (0,1.0) vibrational states as a product of reaction (1), and the observed time dependence of both vibrational states could be satisfactorily simulated by solving the master equation for vibrational relaxation of NH2.This analysis has indicated that the vibrational energy partitioning in the product NH2 is nearly statistical.
Photodissociation dynamics of A state ammonia molecules. II. the isotopic dependence for partially and fully deuterated isotopomers
Mordaunt, David H.,Dixon, Richard N.,Ashfold, Michael N.R.
, p. 6472 - 6481 (1996)
The technique of H(D) Rydberg atom photofragment translational spectroscopy has been used to investigate the photodissociation dynamics of the mixed isotogomers NH2D and NHD2 following the excitation to the v′2 = 0 and 1 levels of their lowest lying A 1B1 (C2v) excited electronic states. Peaks in the resulting total kinetic energy release (TKER) spectra are assigned to levels of the NH2, NHD, or ND2 fragments with a wide range of quantum numbers Ka for rotation about their a inertial axes, and with N = Ka, N = Ka + 1, or N = Ka + 2 as appropriate. These data provide the first measurements of high rotational levels for the ground electronic state of the NHD radical. The least squares fitting of all these spectra, and those resulting from NH3 and ND3, to the best calculated NH2, NHD, and/or ND2 rotational term values provides accurate estimations of the respective N-H and N-D bond dissociation energies D00 across the whole series. These values are D00(H-NH2)=37 115±20 cm-1 (4.602±0.002 eV); D00(H-NHD)=37 240±50 cm-1; D00(H-ND2)=37 300±30 cm-1; D00(D-NHD)=37 880±60 cm-1; and D00(D-ND2)=38 010±20 cm-1. The differences between these values are fully consistent with differences in zero-point energies and lead to a mean value of De=40 510±25 cm-1. Dissociation of NH2D or NHD2 through their (A-X) 20 bands to give an NHD product leads to TKER spectra with a much higher statistical character than those leading to an NH2 or ND2 product, and to those obtained following excitation through the 000 bands. This is rationalized in a semiquantitative manner in terms of a varying contribution to the dissociation rate of the parent molecules from internal conversion (IC) to high levels of their respective ground states. Nuclear permutation symmetry appears to play an important role both for the IC rates and for the subsequent branching between product channels.
The four isotopomer reactions of NH(a) and ND(a) with NH3(X) and ND3(X)
Adam,Hack,Olzmann
, p. 439 - 455 (2007/10/03)
The reactions NH(a) + NH3 (X) → products (1) ND(a) + NH3 (X) → products (2) NH(a) + ND3 (X) → products (3) ND(a) + ND3 (X) → products (4) were studied in a quasi-static reaction cell at room temperature and pressures of 10 and 20 mbar with He as the main carrier gas. The electronically excited reactants NH(a) and ND(a) were generated by laser-flash photolysis of HN3 and DN3, respectively, at λ = 308 nm and detected by laser-induced fluorescence (LIF). Also the ground state species NH(X) and ND(X) as products were detected by LIF. From the measured concentration-time profiles of NH(a) and ND(a) under pseudo-first order conditions, the following rate constants were obtained: k1, = (9.1 ± 0.9) × 1013 cm3 mol-1 s-1 k2 = (9.6 ± 1.0) × 1013 cm3 mol-1 s-1 k3 = (8.0 ± 1.0) × 1013 cm3 mol-1 s-1 k4 = (7.2 ± 0.8) × 1013 cm3 mol-1 s-1. The major products are the corresponding NHi-D2-i(X) radicals (i = 0, 1, 2), whereas quenching processes such as NH(a) + ND3 → NH(X) + ND3 are of minor importance (1%). The isotope exchange NH(a) + ND3 → ND(X) + NHD2 is negligible, and the corresponding channel on the singlet surface NH(a) + ND3(X) → ND(a) + NHD2 (X) contributes with 1% to the overall NH(a) depletion in that reaction. The experimental findings are discussed in terms of a chemical activation mechanism by means of statistical rate theory.
