Dynamical Resonances in Chemical Reactions and Chemical Bonding

瓦伦蒂尼博士得到了物理化学计划的资助，该计划研究气相化学反应中过渡态的结构和动力学。瓦伦蒂尼开发了一种光谱技术，可以间接观察短暂的中间产物(过渡态)，这些过渡态在理论上一直被预测，但在化学反应中从未观察到。瓦伦蒂尼博士的研究涉及对旋转激发截面中所谓的费什巴赫共振的研究，这些截面是在气相中的化学反应中观察到的。直接观测涉及态到态动力学，其中反应物的振动和转动量子态(v，j)是通过自由喷流膨胀冷却制备的，并通过受激拉曼激发进行探测。通过双原子前体的激光光解来选择、改变和精确地指定反应物的碰撞能，以生成反应物原子。利用共振增强多光子电离对单碰撞条件下的反应产物进行了振动和转动(v‘，j’)分析。瓦伦蒂尼博士的研究计划是受到他最近在邻氢、对氢交换反应中发现的费施巴赫共振的推动。这一观察使他能够推断在该反应中发生的线性三原子过渡态的振动能量状态。这一领域的进一步研究将涉及氢-氚交换反应，氯与氯化氢的反应，以及碘和溴与其相应的卤化氢的反应。将获得这些物种的相干拉曼光谱，以阐明理论预测的振动键的性质。

Dr. Valentini is supported by a grant fom The Physical Chemistry Program to study the structure and dynamics of transition states in gas phase chemical reactions. Valentini has developed a spectroscopic technique which permits the indirect observation of the short-lived intermediates (transition states) which have long been theoretically predicted but never observed in chemical reactions. Dr. Valentini's research involves the studies of so-called Feshbach resonances in rotational excitation cross sections which are observed for chemical reactions in the gas phase. The direct observations involve state-to-state dynamics in which the vibrational and rotational quantum states (v,j) of the reactants are prepared by free-jet expansion cooling and probed by stimulated Raman excitation. The collision energy of the reactants is selected, varied, and precisely specified through laser photolysis of a diatomic precursor to generate the reactant atom. Vibrational and rotational (v',j') analysis of the reaction products under single collision conditions are effected using resonance-enhanced multiphoton ionizaiton. Dr. Valentini's research program is motivated by his recent discovery of Feschbach resonances in the ortho-, para-hydrogen exchange reaction. This observation permitted him to infer the vibrational energy states of the linear triatomic transition state which occurs in this reaction. Further studies in this area will involve the hydrogen deuterium exchange reaction, the reaction of chlorine with hydrogen chloride, and the reaction of iodine and bromine with their corresponding hydrogen halides. Coherent Raman spectra of these species will be obtained to elucidate the nature of the theoretically predicted vibrational bonding.