17778-88-0Relevant articles and documents
Ultralow temperature kinetics of neutral-neutral reactions. The technique and results for the reactions CN+O2 down to 13 K and CN+NH3 down to 25 K
Sims, I. R.,Queffelec, J.-L.,Defrance, A.,Rebrion-Rowe, C.,Travers, D.,et al.
, p. 4229 - 4241 (1994)
An entirely new experimental method is described which enables the rate constants of neutral-neutral gas-phase reactions to be measured at ultralow temperatures.The measurements are made by applying the pulsed laser photolysis (PLP), laser-induced fluorescence (LIF) technique of studying the kinetics of free radical reactions in the ultracold environment provided by the gas flow in a Cinetique de Reaction en Ecoulement Supersonique Uniforme (CRESU) apparatus.The experimental method is described in some detail and its application and limitations are discussed.Results are reported for the reactions of CN radicals with O2 and NH3.For reaction (1) between CN and O2 data are reported for the temperature range T=13-295 K and the rate constants are well-matched by the expression k1(T)=(2.49+/-0.17)*10-11 (T/298)(-0.63+/-0.04) cm3 molecule-1 s-1.For reaction (2) between CN and NH3, rate constants in the temperature range T=25-295 K fit the expression k2(T)=(2.77+/-0.67)*10-11 (T/298)(-1.14+/-0.15) cm3 molecule-1 s-1.The kinetic data are discussed in terms of the latest quantum chemical and reaction rate theories for these systems.
Formation and characterization of VUV photolytically-induced (NH 2)(NH3)n aggregates, 0 ≤ n ≤ 3
Zins,Krim
, p. 10285 - 10295 (2013/09/02)
The formation of amidogen radical may be an important precursor toward the formation of prebiotic molecules on the surface of ice grains in interstellar clouds. Many laboratory experiments aimed at characterizing the photolysis of ammonia. Wide shifts wer
Thermochemistry is not a lower bound to the activation energy of endothermic reactions: A kinetic study of the gas-phase reaction of atomi-chlorine with ammonia
Gao, Yide,Alecu,Hsieh,Morgan, Brad P.,Marshall, Paul,Krasnoperov, Lev N.
, p. 6844 - 6850 (2008/10/09)
The rate constant for Cl + NH3 → HCl + NH2 has been measured over 290-570 K by the time-resolved resonance fluorescence technique. Ground-state Cl atoms were generated by 193 nm excimer laser photolysis of CCl4 and reacted under pseudo-first-order conditions with excess NH3. The forward rate constant was fit by the expression k1 = (1.08 ± 0.05) × 10-11 exp(-11.47 ± 0.16 kJ mol-1/RT) cm3 molecule-1 s-1, where the uncertainties in the Arrhenius parameters are ±1 σ and the 95% confidence limits for k1 are ±11%. To rationalize the activation energy, which is 7.4 kJ mol -1 below the endothermicity in the middle of the 1/T range, the potential energy surface was characterized with MPWB1K/6-31++G(2df,2p) theory. The products NH2 + HC1 form a hydrogen-bonded adduct, separated from Cl + NH3 by a transition state lower in energy than the products. The rate constant for the reverse process k-1 was derived via modified transition state theory, and the computed k-1 exhibits a negative activation energy, which in combination with the experimental equilibrium constant yields k1 in fair accord with experiment.
Radiolytic Reactions of Monochloramine in Aqueous Solutions
Poskrebyshev,Huie,Neta
, p. 7423 - 7428 (2007/10/03)
Monochloramine reacts with hydrated electrons very rapidly, k(NH 2Cl+eaq-) = (2.2 ± 0.3) × 10 10 L mol-1 s-1, to produce .NH 2 radicals. It reacts with .OH radicals more slowly, k(NH2Cl+.OH) = (5.2 ± 0.6) × 108 L mol-1 s-1, to produce .NHCl radicals. While .NH2 exhibits an absorption peak at 530 nm, with a molar absorption coefficient ε530 = 80 L mol-1 cm -1, .NHCl exhibits two peaks at 330 and 580 nm, ε330 = (85 ± 30) L mol-1 cm-1 and ε580 = (56 ± 30) L mol-1 cm-1. The .NHCl radical undergoes self-decay and can react also with O 2 to form a peroxyl radical. It is suggested that the peroxyl radical exists in equilibrium NHClO2? NHCl + O2 with an estimated equilibrium constant of (3 ± 2) × 10 -3 mol L-1. The reaction of chloramine with the carbonate radical is suggested to form a complex [CO3NH2Cl] .- with kf = 2.5 × 105 L mol-1 s -1 and kr = 4 × 102 s-1, and this complex decomposes with k = 7 × 102 s-1 to form .NHCl.
Product branching ratios of the NH2(X2B1) + NO2 reaction
Lindholm, Ned,Hershberger, John F.
, p. 4991 - 4995 (2007/10/03)
The reaction of NH2(X2B1) with NO2 was studied at 298 K using time-resolved infrared diode laser spectroscopy to detect N2O and NO products. The N2O + H2O channel was confirmed to be a rather minor contribution to the overall reaction, with a branching ratio of 0.24 ± 0.04. The branching ratio of the NO + H2NO channel was measured to be 0.76 ± 0.1.
Kinetics of the reactions of NCO radicals with NO and NH3
Becker,Kurtenbach,Schmidt,Wiesen
, p. 128 - 133 (2007/10/03)
The rate constants for the reaction of NCO (X2∏) radicals with NO and NH3 were measured at 20 Torr total pressure in temperature ranges of 290-1098 K and 295-882 K, respectively, using C1NCO excimer laser photolysis for NCO radical formation in combination with laser-induced fluorescence detection of NCO. In the temperature range investigated the NCO + NO reaction exhibits a negative temperature dependence which is described by the following three parameter Arrhenius equation: (Equation Presented) with E0 in units of kJ/mol. For the NCO + NH3 reaction the measurements exhibit a positive temperature dependence over the temperature range investigated with a slight upwards curvature. A modified three parameters Arrhenius fit provides a good description of the experimental data: (Equation Presented) with E0 in units of kJ/mol. In addition, the rate constant of the NCO + NH3 reaction was found to be pressure independent in the range 10-193 Torr at 295 K. VCH Verlagsgesellschaft mbH, 1997.
308 nm laser photodissociation of HN3 adsorbed on Si(111)-7×7
Bu, Y.,Lin, M. C.
, p. 118 - 128 (2008/10/08)
The photodissociation of HN3 adsorbed on Si(111)-7×7 at 308 nm was investigated using HREELS and XPS. Species such as NHx N2, and N3 were identified on the surface with comparable concentrations after the irradiation with 1×1020 photons of a 10 L HN3 dosed Si(111) surface. The N3 species showed two stretching modes at 178 and 255 meV, while that of the N2 appeared at 206 meV in HREELS. The formation of these products was also corroborated by the corresponding XPS results. Further laser irradiation caused the dissociation and partial desorption of the adsorbates with NHx left on the surface. Annealing the post-irradiated sample to 500 and 800 K resulted in the breaking of the NH bond and the desorption of the H-species, while the atomic N remained on the surface forming silicon nitride. The possibility of using HN3 for laser-induced chemical vapor deposition of Si3 N4 and group-III nitrides at low temperatures is suggested.
Laser Induced Fluorescence Studies of the Reactions of NH(a1Δ) with NO and HCN
Hack, W.,Rathmann, K.
, p. 4155 - 4161 (2007/10/02)
The reactions of electronically excited imidogen NH(a1Δ) with NO and HCN have been studied at room temperature and low total pressures (20 mbar): NH(a) + NO --> products (1): NH(a) + HCN --> products (2).NH(a), produced by laser photolysis of HN3 at λL = 308nm, was detected directly by laser-induced fluorescence (LIF).Measurements of the rate constants were performed under pseudo-first-order conditions, i.e., >> a)>, whereby the time resolution resulted from the delay between the photolysis and the probe lasers.The following rate constants were measured at T = 298 K: k1 = 1.7*1013 cm3/(mol s); k2 = 2.1*1013 cm3/(mol s).Direct detection of the primary products NH(X), OH(X), NH2(X), CH2(a1A1), and CN(X) was performed by LIF.The contribution of physical quenching of NH(a) to form NH(X) for reactants NO and HCN was found to be 40percent and 4percent respectively.In reaction 1 OH and in reaction 2 CN were detected as chemical products.
Elementary Reactions of NH(a1Δ) with Polyatomic Molecules
Hack, W.,Wilms, A.
, p. 107 - 122 (2007/10/02)
The gas phase reactions of NH(a1Δ) with six polyatomic molecules R = HN3, H2O, N2O, NO2, CO2 and C6H6 (benzene) have been studied NH(a1Δ) was generated by laser photolysis of HN3 at λL = 248 nm.The removal of NH(a1Δ) by the reactant R was observed directly with the laser-induced fluorescence (LIF).The removal rate constants k1(R) at room temperature were measured: k1(HN3) = 7.3E13, k1(H2O) = 2.9E13, k1(N2O) = 1.0E12, k1(NO2) = 2.2E13, k1(CO2) = 1.4E11, and k1(C6H6) = 1.0E14 (in cm3/mol s).The contribution of intersystem crossing and of chemical reaction to the reaction products has been investigated quantitatively by the direct detection of the product NH(X3 Σ-) with the LIF.The branching ratios of intersystem crossing are: 6percent, /= 50percent and /= 2percent for H2O and N2O respectively. - Keywords: Chemical kinetics / Elementary reactions / Photochemistry
Reaction between the Amidogen Radical, .NH2, and Molecular Oxygen in Low-Temperature Matrices
Crowley, John N.,Sodeau, John R.
, p. 4785 - 4790 (2007/10/02)
The reaction between .NH2 and O2 has been examined in a low-temperature matrix for the first time.Results from a series of experiments employing isotopically substituted ammonia and oxygen indicate that the primary reaction products are HONO and H atoms.A reaction mechanism is proposed that involves the intermediacy of the aminoperoxy radical, NH2OO., which is stabilized by the low-temperature/high-pressure environment of the matrix before undergoing intramolecular decomposition or reaction with oxygen.
