12596-60-0Relevant articles and documents
308 nm laser photodissociation of HN3 adsorbed on Si(111)-7×7
Bu, Y.,Lin, M. C.
, p. 118 - 128 (1994)
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.
Okabe,Mele
, p. 2100,2105 (1969)
Design and characterization of a synthetic electron-transfer protein
Kornilova, Anna Y.,Wishart, James F.,Xiao, Wenzhong,Lasey, Robin C.,Fedorova, Anna,Shin, Yeon-Kyun,Ogawa, Michael Y.
, p. 7999 - 8006 (2000)
A 30-residue polypeptide [H21(30-mer)] with the sequence Ac-K(IEALEGK)2(IEALEHK)-(IEALEGK)G-NH2 was synthesized. The circular dichroism (CD) spectrum of the peptide shows minima at 208 and 222 nm and θ222/θ208 = 1.06, which indicates the formation of a self-assembled coiled-coil when dissolved in aqueous solution. The concentration dependence of the CD data can be fit to an expression that describes a two-state monomer - dimer equilibrium for the apopeptide(K(d) = 1.5 ± 0.4 μM and θ(max) = -23 800 ± 130 deg cm2 dmol-1), showing that it has a maximum helicity of 69%. A [MTSL-C21(30-mer)] dimer was also prepared in which MTSL is the thiol-specific nitroxide spin label 1-oxyl-2,2,5,5-tetramethyl-Δ3-pyrroline-3-methyl-methanethiosulfonate attached to C21 of the 30-mer. Fourier deconvolution analysis of the dipolar line broadening of the electron paramagnetic resonance (EPR) spectrum yields a measure of the interchain Cα - Cα distance of 13.5 ± 0.9 A at position 21 of the coiled-coil, which is nearly identical to those distances observed for the isostructural family of bZip proteins. Two metallohomodimers, [Ru(trpy)(bpy)-H21(30-mer)]2 and [Ru(NH3)5-H21(30-mer)]2, in which the ruthenium complexes were coordinated with the H21 site of the 30-mer, were prepared. Sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS - PAGE), chemical cross-linking studies, and analytical ultracentrifugation show that the peptides exist as a dimeric coiled-coil with a molecular weight of ~ 7.5 kDa. The electron transfer (ET) heterodimer, [Ru(trpy)(bpy)-H21 (30-mer)]/ [Ru(NH3)5-H21(30-mer)], was prepared, and molecular modeling shows that the two metal complexes are separated by a metal-to-metal distance of ~ 24 A across the noncovalent peptide interface. Pulse radiolysis was used to measure an ET rate constant of k(et) = 380 ± 80 s-1 for the intracomplex electron transfer (ΔG°= -1.11 eV) from the Ru(II)(NH3)5-H21 donor to the Ru(III)(trpy)(bpy)-H21 acceptor. The value for k(et) falls within the range reported for modified proteins over comparable distances and supersedes the one reported in an earlier communication.
The Redox Potential of the Azide/Azidyl Couple
Alfassi, Zeev B.,Harriman, Anthony,Huie, Robert E.,Mosseri, S.,Neta, P.
, p. 2120 - 2122 (1987)
Pulse radiolysis experiments were carried out with neutral aqueous solutions containing azide with iodide, bromide, or thiocyanate to examine possible one-electron transfer rates and equilibria involving the N3 radical/N3(1-) couple.The N3 radical was found to oxidize I(1-) with a rate constant of 4.5E8/M*s.No reaction was observed between I2(1-) radical and N3(1-).With Br(1-), however, the system reached equilibrium, Br2(1-) radical + N3(1-)->f = 4.0E8/M*s and kr = 7.3E3/M2*s.From the equilibrium constant K = 5.5E4 M and the redox potential E(Br2(1-) radical/2Br(1-)) = 1.63 V we calculated E(N3 radical/N3(1-)) = 1.35 +/- 0.02 V vs.NHE.Cyclic voltammetry experiments with N3(1-) showed a single peak on the anodic scan and no peak on the cathodic scan due to the rapid decay of the N3 radicals.From the dependence of peak potential on scan rate we derived E1/2 for the N3 radical/N3(1-) couple, 1.32 /- 0.03 V vs.NHE.
Observation of N3 by Laser-Induced Fluorescence
Beaman, R. A.,Nelson, T.,Richards, D. S.,Setser, D. W.
, p. 6090 - 6092 (1987)
Gas-phase N3 was generated by the F + NH3 reaction and detected by using laser-induced fluorescence in a flow reactor.The and the excitations were investigated.Evidence was obtained for an upper-state lifetime of level or the smaller spin-orbit splitting in the level can be utilized for monitoring of N3 by the LIF technique using a monochromator to disperse the fluorescence.Very weak transitions were identified, and these could be useful for monitoring the laser-induced fluorescence of N3 with an interference filter.
Ultraviolet photodissociation dynamics of HN3: The H+N3 channel
Zhang, Jingsong,Xu, Kesheng,Amaral, Gabriel
, p. 285 - 290 (1999)
The H+N3(X 2Πg) channel in the ultraviolet photodissociation of HN3 has been studied at 248.3 and 193.3 nm using the high-n Rydberg H-atom time-of-flight technique. In 248.3 nm photodissociation, center-of-mass translational energy distribution reveals a propensity toward product translation (〈ftrans〉=0.71) and N3 bending and symmetric stretching excitation. An anisotropic product angular distribution (β≈-0.8) indicates a perpendicular electronic transition and rapid dissociation on the excited-state surface. H-N bond energy is estimated: D0(H-N3)≤88.7±0.5 kcal/mol. At 193.3 nm, 〈ftrans〉 is smaller and product angular distribution is energy-dependent, suggesting multiple dissociation pathways via different electronic states.
A molecular beam study of the H + N3 reaction. Product NH internal state distribution and electronic state branching ratio
Chen, Jing,Quinones, Edwin,Dagdigian, Paul J.
, p. 4033 - 4042 (1990)
The H + N3 -> NH(X3Σ-, a1Δ, b1Σ+) + N2 reaction has been studied in a molecular beam-gas scattering arrangement in order to determine the nascent product state distribution.The NH product in specific rovibronic/fine-structure states has been detected by laser fluorescence excitation.The relative cross sections for formation of various vibrational levels in the a1Δ electronic state were determined to equal 1:1.0 +/- 0.3:1.4 +/- 0.3:1.5 for v = 0 through 3, inclusive, while the v = 0 to v = 1 population ratio in the X3Σ- state was found to be 1:0.015 +/- 0.003.The rotational distributions in all vibronic levels were found to be characterized by temperatures near 300 K, suggestive of relaxation of the nascent rotational distributions.By comparison of the populations of a specific pair of X3Σ- and a1Δ state levels and with summation over the derived rovibrational distributions, an electronic state branching ratio of 3.2 +/- 1.3 was obtained for the X3Σ- to a 1Δ electronic state branching ratio.An upper limit of 0.02 was also derived for the ratio of the b1Σ+ v = 0 to a1Δ v = 0 populations.These results are compared with NH fragment distributions observed in the photodissociation of HN3(X1A') and with our expectations based on our fragmentary knowledge of HN3 potential energy surfaces.
