15117-84-7Relevant academic research and scientific papers
State to state recoil anisotropies in the photodissociation of deuterated ammonia
Mordaunt, David H.,Ashfold, Michael N. R.,Dixon, Richard N.
, p. 7659 - 7662 (1998)
The near ultraviolet photodissociation of deuterated ammonia, ND3, allows particularly clear observation and quantification of the quantum state dependent angular anisotropy of the recoiling D+ND2(X) photoproducts. The recoil anisotr
Photodissociation dynamics of A state ammonia molecules. I. State dependent μ-V correlations in the NH2(ND2) products
Mordaunt, David H.,Ashfold, Michael N.R.,Dixon, Richard N.
, p. 6460 - 6471 (1996)
The H(D) Rydberg atom photofragment translational spectroscopy technique has been applied to a further detailed investigation of the photodissociation dynamics of NH3 and ND3 molecules following excitation to the lowest two (v2=0 and 1) vibrational levels of the first excited (A 1A′2) singlet electronic state. Analysis of the respective total kinetic energy release spectra, recorded at a number of scattering angles Θ [where Θ is the angle between the ε vector of the photolysis photon and the time-of-flight (TOF) axis], enables quantification of a striking, quantum state dependent, μ-v correlation in the NH2(ND2) products. The spatial distribution of the total flux of H(D) atom photofragments is rather isotropic (βlab～0)- However, more careful analysis of the way in which the TOF spectra of the H(D) atom photofragments vary with Θ reveals that each H+NH2(D+ND2) product channel has a different partial anisotropy parameter, βlab(v2,N), associated with it: The H(D) atom ejected by those molecules that dissociate to yield NH2(ND2) fragments with little rotational excitation largely appear in the plane of the excited molecule (i.e., perpendicular to the transition moment and the C3 axis of the parent, with β tending towards -1). Conversely, the H(D) atoms formed in association with the most highly rotationally excited partner NH2(ND2) fragments tend to recoil almost parallel to this C3 axis (i.e., β→+2). Such behavior is rationalized in the context of the known potential energy surfaces of the A and X states of ammonia using a classical, energy and angular momentum conserving impact parameter model in which we assume that all of the product angular momentum is established at the point of the conical intersection in the H-NH2(D-ND2) dissociation coordinate. We conclude by reemphasizing the level of care needed in interpreting experimentally measured β parameters in situations where there is averaging over either the initial (parent) or final (product) quantum states.
Microwave optical double resonance spectroscopy of ND2 in (000) of X2B1
Cook, J. M.,Hills, G. W.
, p. 2144 - 2153 (1983)
Microwave optical double resonance spectroscopy has been used observe in excess of 200 microwave transitions involving 21 rotational levels in the (000), X2B1 state of ND2.The obseved transitions have been fitted to two model Hamilto
State selective photodissociation dynamics of state ammonia. II
Biesner, J.,Schnieder, L.,Ahlers, G.,Xie, Xiaoxiang,Welge, K. H.,et al.
, p. 2901 - 2911 (1989)
The photodissociation dynamics of state ammonia molecules (both NH3 and ND3) has been further investigated using the technique of H(D) atom photofragment translational spectroscopy.The resulting NH2 (ND2) fragments are observed to carry high levels of
The effect of parent zero-point motion on the ND 2 ( ? ) rotational state distribution in the 193.3 nm photolysis of ND 3
Reid, Jonathan P.,Loomis, Richard A.,Leone, Stephen R.
, p. 240 - 248 (2000)
The vibrational and rotational product-state distributions of ND2(?2A1) has been probed following the photodissociation of ND3 at 193.3 nm by time-resolved Fourier Transform infrared emission spectroscopy. The dynamics of the bond cleavage are inferred from the product state distributions by comparison with an earlier study of the photodissociation of NH3. The degree of excitation about the minor rotational b/c-axes of the product is attributed to the amount of zero-point energy of the parent molecule in the ν4 H-N-H (D-N-D) scissors bending coordinate of the NH3/ND3(?) predissociative state. A bimodal ND2(?2A1) distribution is observed for rotation about the primary a-axis, analogous to the NH2 fragment formed in the photodissociation of NH3.
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.
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 (2007/10/03)
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.
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 (2007/10/02)
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.
A High-Temperature Photochemistry Study of the D + ND3 Reaction
Marshall, Paul,Fontijn, Arthur
, p. 6297 - 6299 (2007/10/02)
The kinetics of the D + ND3 reaction (2) has been studied from 590 to 1220 K by using the high-temperature photochemistry (HTP) technique.D(12S) atoms were generated by flash photolysis of ND3 and monitored by time-resolved atomic resonance fluorescence with pulse counting. k2(T) is determined to be 3.2 x 1E-10 exp(-8810 K/T) cm3 molecule-1 s-1.Accuracy assessments are discussed in the text.Comparison to k1(T) for H + NH3 (1) measured in the same apparatus and over a similar temperature range shows that k2(T) is smaller. k1(T) and k2(T) agree reasonably well with calculations based on transition-state theory and a simple tunneling model using the same potential energy surface for both reactions.Considered alone, k2(T) can also be modeled without tunneling.
Energy disposal in the reactions O(1D) + NH3 -> OH + NH2 and O(1D) + ND3 -> OD + ND2
Cordova, Jose F.,Rettner, Charles T.,Kinsey, James L.
, p. 2742 - 2748 (2007/10/02)
Further investigations of the reaction O(1D) + NH3 -> OH + NH2 and the first results on the reaction O(1D) + ND3 -> OD + ND2 are reported.The OH and OD rotational distributions have been found to be statistical.Hotter than statistical vibrational distributions are measured.The spin state distribution is statistical, with a strong preference to populate the energetically lower Λ component in both spin states.A preliminary study of the NH2 product shows very little rotational excitation.An analysis of this radical's vibrational hot bands was not carried out due to lack of detailed spectroscopic information.The total energy is found to be partitioned according to R(OH)> ca. 0.1, V(OH)> ca. 0.25, R(NH2)> ca. 0.04, and T> ca. 0.25.
