An experimental and theoretical study of ring closing dynamics in HN3

We report on an H(D)-atom Rydberg tagging experiment for H(D)N(3) photolysis providing detailed dynamical information on the wavelength dependence of the H(D) + N(3) channel. We observe subtle yet striking changes in the photochemical dynamics as the photolysis energy passes through approximately 5.6 eV. In addition to producing linear azide with an average of approximately 40% of available energy appearing as translation, a second H(D)-atom producing channel grows in above this energy releasing only about 15%. An observed (inverse) isotope effect suggests that statistical decomposition on S(0) is unimportant. High level ab initio quantum chemical calculations reveal a transition state to cyclization of the N(3) moiety in H(D)N(3) on the first excited singlet (S(1)) surface that is close in energy to the experimentally observed threshold energy for this "slow channel". Furthermore, the translational energy release of the "slow channel" is energetically consistent with cyclic-N(3) formation. This work provides the clearest presently available insights into how ring closure can occur in azide photochemistry.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.     

HN3分子在190-248 nm的紫外光分解动力学

利用氢原子里德堡态飞行时间谱技术研究HN3分子在紫外光(190?248 nm)光照射下的H+N3通道的光解动力学结果．通过测量H+N3通道的产物平动能分布以及产物的角分布，得到了在不同波长光解下N3产物分子的振动态分布． 实验结果表明， 在大于225 nm时，HN3分子主要是通过一个排斥态解离的．而在低于225 nm时，有一个慢的通道从220 nm 开始出现．这一新的解离通道是一个闭环产生环状N3产物的通道．当光解能量增加时，这一新通道相对的变得越来越重要．     

Astrophysical S-factors from asymptotic normalization coefficients

S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which provide the normalization of the tail of the overlap function. For example the overlap for ⁸B → ⁷Be+p defines the S-factor for ⁷Be (p, γ)⁸B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of the technique, the ¹⁶O(³He, d)¹⁷F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ¹⁷F. The S-factors for ¹⁶O(p, γ)¹⁷F calculated from these ¹⁷F → ¹⁶O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same technique, the ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the asymptotic normalization coefficient for ⁷Be(p, γ)⁸B. This result provides an indirect determination of S ₁₇(0).     

Gas-phase deprotonation of arylalkylamines. A collision-induced dissociation study

The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd.     

Isolation of NO(3)(-)-N as 1-phenylazo-2-naphthol (Sudan-1) for measurement of delta(15)N

The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd.