Rate Constants For N2 Research Articles

Thermal Decomposition Mechanism of Nitroglycerin by ReaxFF Reactive Molecular Dynamics Simulations

ABSTRACT The decomposition processes of nitroglycerin (NG) at various temperatures (2500, 2750, 3000, 3250 and 3500 K) are simulated by the reactive molecular dynamics simulations with ReaxFF-lg. The initial decomposition pathway of NG, the evolution of the main products and the reaction kinetic parameters for the different stages are analyzed. The results show that the main initial decomposition mechanisms of NG are O-NO2 bond dissociation and the hydrogen capture reaction of NO2. The main products of NG thermal decomposition are NO2, NO, HNO, CO2, N2, and H2O, while CO2, N2, and H2O are the final products. As the temperature increases, the processes of O-NO2 bond dissociation and the hydrogen capture reaction of NO2 accelerate, resulting in accelerated decomposition of NG. The reaction kinetic parameters are calculated for three different reaction stages. The activation energy and the pre-exponential factor obtained in the initial decomposition stage are 69.58 kcal mol−1 and 32.53 s−1. The activation energy and the pre-exponential factor obtained in the intermediate decomposition stage are 111.78 kcal mol−1 and 29.12 s−1. At 3250 K, the rate constants of N2 and CO2 reach maximum while the rate constant of H2O increases continuously with increasing temperature. Accordingly, the mechanism of initial thermal decomposition of NG under the high temperatures is proposed detailedly.

Novel Effect of H2O on the Low Temperature Selective Catalytic Reduction of NO with NH3 over MnOx—CeO2: Mechanism and Kinetic Study

H2O generally shows a strong inhibition on the low temperature selective catalytic reduction (SCR) reaction. However, a novel phenomenon was discovered that the low temperature SCR reaction over MnOx—CeO2 was promoted by H2O. The rate constants of N2 and N2O formation over MnOx—CeO2 were calculated using the steady-state kinetic study. It showed that both the rate constants of N2 and N2O formation decreased in the presence of H2O, and the promotion of the SCR reaction over MnOx—CeO2 by H2O was mainly attributed to the inhibition of N2O formation. Meanwhile, the influence of H2O on the elementary reaction of N2O formation over MnOx—CeO2 was studied using the transient reaction study. It indicated that the inhibition of N2O formation over MnOx—CeO2 by H2O was not only attributed to the competition adsorption of H2O with NH3 but also related to the decrease of the oxidation ability of MnOx—CeO2 in the presence of H2O.

Kinetics of the nitrogen first negative system excitation by ionising radiation

The rate constants of N2+(B) quenching by nitrogen and helium and of two- and three-body charge exchange of He2+ on H2, D2, and Kr are measured from luminescence at the 0–0 transition of the first negative system of nitrogen in mixtures of helium and nitrogen with hydrogen, krypton or deuterium excited by alpha particles emitted by 210Po .

Experimental and theoretical determination of rotational-translational state-to-state rate constants for N2:He collisions at low temperature (3<T<20 K)

We present an experimental determination of state-to-state rotational–translational (RT) rate constants of N2:He collisions in the vibrational ground state as a function of temperature in the range 3<T<20 K. Raman spectroscopy in supersonic expansions of N2/He mixtures is used to determine the primary data that, together with the N2:N2 state-to-state RT rates previously determined [Ramos et al., Phys. Rev. A 66, 022702 (2002)], are needed to solve the master equation according to a procedure that does not impose any particular scaling law. We also report first principle calculations of the N2:He state-to-state RT rate constants performed using the full three-dimensional potential energy surface of Reid et al. [J. Chem. Phys. 107, 2329 (1997)], in the 3<T<300 K temperature range. The coupled-channel method, and the coupled-states approximation, were applied in the low (0–610 cm−1) and in the high (610–1500 cm−1) energy limits, respectively. A good agreement between theoretical and experimental results is found in the temperature range where comparison is possible.

Rate constants for deactivation of N2(A) v=2–7 by O, O2, and NO

Rate constants for N2(A,v) quenching by O, for levels v=2–7, by O2 for levels v=3–7, and by NO for levels v=2–4, have been measured in this work. This is the first data set for the quenching by O of vibrational levels v>3. The results of this work are based on the measurement by laser induced fluorescence (LIF) of N2(A,v) decay in a rf pulsed postdischarge, supported by LIF measurements of NO density. O atom density is deduced by N2(A,v=0,1) decay using the known rate constants of N2(A,v=0,1) quenching by O, O2, and NO. Finally, from appropriate scaling of LIF results for the various v levels, N2(A,v) vibrational distributions are deduced, showing a quite low vibrational excitation of the triplet metastable, characterized by an average Boltzmann vibrational temperature of the order of 2000–2500 K with some superimposed structures.

Adiabatic channel study of the capture of nitrogen and oxygen molecules by an ion: effect of nuclear symmetry and spin-spin interaction

Within the adiabatic channel treatment of ionmolecule capture we have calculated the low temperature capture rate constants of N2(1Σg+) and O2(3Σg−)in collisions with positive and negative ions. In both cases, the charge-quadrupole and the anisotropic charge-induced dipole interactions produce noticeable deviations from the Langevin rate constant. The rate constants calculated with account for the anisotropic interaction, in addition, are substantially affected by nuclear symmetry; in the case of O2(3Σg−), the fine-structure spin-spin interaction strongly manifests itself in the rate constants.

Buffer gas effect on the detection of iodine by laser induced fluorescence

Laser-induced fluorescence (LIF) coupled with photon-counting technique to detect molecular iodine at ultratrace level is reported. Electronic quenching rate constants for N2, NO2 and H2O, as well as for the mixture of NO2 and H2O has been measured. The application of the LIF method to monitoring129I2 in spent fuel reprocessing off-gas streams is evaluated.

Improvements in the generation and detection of Kr(3P) and Kr(3P2) atoms in a flow reactor: Decay constants in He buffer and total quenching rate constants for Xe, N2, CO, H2, CF4, and CH4

The generation and decay of Kr(3P2) and Kr(3P0) atoms in a flowing afterglow reactor at 300 K using He carrier gas have been characterized and compared with Ar carrier gas. The dominant loss for the Kr(3P2) and Kr(3P0) atoms in He is diffusion to and quenching at the wall; the two-body quenching constants are of the order of 1×10−15 cm3 s−1 for each. The Kr(3P0) concentration in He carrier was sufficiently high that the total quenching rate constants were measured without resorting to optical pumping from the lower energy Kr(3P2) state. Room temperature rate constants are reported and the product states are discussed for the Kr(3P2) and Kr(3P0) reactions with Xe, CO, N2, H2, CF4, and CH4; the difference between the Kr(3P0) and Kr(3P2) rate constants for N2 is nearly a factor of 6. Quenching rate constants for 13CO are ∼25% smaller than those for 12CO. The Kr(3P0) reaction with CO gives mainly CO(b 3Σ+) and (e 3Σ−); the CO(b, v′=0) level is much more rotationally excited than CO(b, v′=1). Excitation-transfer to Xe from Kr(3P2) gives mainly Xe(6p[3/2]2 and [3/2]1 ); the Kr(3P0) reaction favors the Xe(7s) states. A systematic study of the best electrode configuration and operating conditions for the dc discharge using He carrier gas is reported for the generation of Xe(3P2), Ne(3P0) and Ne(3P2), as well as Kr(3P2) and Kr(3P0).

Rate coefficient for the gas phase reaction of NaOH with CO2

The third‐order rate constants for NaOH + CO2 + M were measured in a flow tube at 298 K. The rate constants for N2 and N2O buffer gases are (1.3±0.3) × 10−28 and (2.9±0.6) × 10−28 cm6 molecule−2 s−1, respectively. We expect the product of this reaction, NaHCO3, to be relatively stable with respect to 0 atom reaction and photolysis and to be a dominant reservoir species for Na in the mesosphere. The association reaction of NaOH with CO2 is at least 40 times faster than NaOH + HCl at all altitudes below the Na layer. Na species will not affect stratospheric ClOx and O3 chemistry.

Quenching rate constants for CO(a3Π; ν′=0,1,2)

The quenching rate constants for CO (a 3Π; ν′=0,1,2) with H2, D2, N2, O2, NO, CO, CO2, COS, CS2, SO2, NH3, C2N2, CH4, C2H2, C2H4, C2H6, C2F6, and SF6 have been measured in a discharge-flow apparatus. The sources of CO(a 3Π) were the interaction of Ar(3P0, 2) or He(23S) atoms with carbon dioxide. The bimolecular-quenching coefficients are [inverted lazy s] 10−10 cm3 sec−1, except for N2, CO2, C2F6, and SF6, which range from 10−11 to 10−12 cm3 sec−1. Only the rate constants for N2, CO, and CS2 showed a dependence upon the vibrational excitation of CO(a). For these reagents, the mechanism for quenching is discussed; the reaction with N2(X) yields significant amounts of N2(A). The CO(a) + NO(X) reaction is of particular interest because the β- and γ-band emission can be used to identify the NO(A and B) products and to provide a diagnostic test for the presence of CO(a 3Π). The reaction between N2(A 3 Σu+; ν′=0,1) and CO(X) is discussed in an appendix.