由激光诱导荧光方法探测光碎片分子取向的理论研究

采用密度矩阵方法，推导了从激光诱导荧光（LIF）强度中抽出光碎片取向参数的表达式。光碎片的取向由分子态多极矩描述。用于解离母分子和激发碎片分子的激光均为线偏振光，而探测荧光为非偏振光。激光诱导荧光强度是光碎片分子初始态多极矩、线强度因子和解离-激发几何因子的函数。光碎片的取向参数可测量荧光偏振比和计算动力学因子而获得

OH Produced from o-nitrophenol photolysis: A combined experimental and theoretical investigation

As an important class of nitroaromatic compounds, nitrophenols are of particular interest since their presence in the environment has been acknowledged. Much work on the occurrence of nitrophenols in the environment, both in the gas and in the condensed phase, has been done, and nitrophenols have been discovered in different atmospheric compartments, such as ambient air, clouds, fog, and snow. Moreover, previous spectroscopic studies revealed that the strong absorption band of nitrophenols is in the atmospherically relevant UV region (300-400 nm), implying the photochemistry of nitrophenols might be important for the atmosphere. In the present work, photodissociation dynamics of o-nitrophenol (HOC6H4NO2) in the gas phase at different photolysis wavelengths (361-390 nm) is investigated, and the nascent OH radical is observed by the single-photon laser-induced fluorescence (LIF) technique. At all photolysis wavelengths, the OH radicals are formed in vibrationally cold state (υ″ = 0), and have similar rotational state distributions. The average rotational temperature for all photolysis wavelengths is approximately 970 ± 120 K, corresponding to a rotational energy of 1.9 ± 0.2 kcal mol-1. The spin-orbit and Λ-doublet states of the OH fragments formed in the dissociation are measured to be nonstatistical distributions. To get an insight into the dissociative mechanism leading to OH formation in the photolysis of o-nitrophenol, the potential energy surfaces of the OH-forming channels are mapped by ab initio theoretical calculations. According to both experimental and theoretical results, a possible mechanism for OH formation is proposed. It is suggested that electronically excited o-nitrophenol mostly relaxes to the lowest excited triplet state (T1) via intersystem crossing followed by intramolecular H transfer to form an aci-nitro isomer, from which OH elimination takes place by N-OH bond cleavage most likely. The transition state for the N-OH bond rupture channel is located on the T1 state and characterization of the dissociative state to be T1 state strongly supports much of our experimental findings

Photodissociation Dynamics of o-Nitrobenzoic Acid

Photodissociation dynamics of o-nitrobenzoic acid at 295 and 355 nm was studied by probing the nascent OH photoproduct employing the single-photon laser induced fluorescence technique. At both the photolysis wavelengths, the OH fragments are found to be vibrationally cold but have different rotational state distributions. Upon photolysis at 295 nm, the relative population of OH in different rotational states does not follow Boltzmann equilibrium distribution, whereas upon photolysis at 355 nm, a perfect Boltzmann distribution is observed with a rotational temperature of 1010 ± 100 K. Between the two spin-orbit states, 2Π3/2 and 2Π1/2, the former is found to be preferentially populated and the distribution of the Π(A′) state for the Λ-doublet is dominant at both the wavelengths studied. Several possible dissociation pathways of o-nitrobenzoic acid leading to formation of the OH fragment were investigated computationally. Based on the theoretical and experimental studies, a possible mechanism of OH formation from the photodissociation of o-nitrobenzoic acid at 295 and 355 nm is proposed

亚硝基苯光解过程中的能量配置

利用单光子激光诱导荧光（LIF）技术，测量了亚硝基苯(C_6H_5NO)初生态光解碎片NO(X~2II v" = 1, 2, 3)的转动光谱。通过对初生态光解碎片NO(X~2II)内能态布居的分析，得到了NO(X~2II)的转动温度和相对振动布居比，研究了亚硝基苯在266 nm激光光解过程中的能量配置情况。与小分子相比，大的亚硝基苯分子，其光解过程中能量分布很宽，涉及到所有自由度

激光烧蚀叠氮化钠产生的团簇离子及其分布

用飞行时间质谱研究了激光烧蚀叠氮化钠固体产生的正负团簇离子的组成及其分布，产生的团簇系列包括：（Ｎａ（ＮａＮ３）ｎ）＾＋，（Ｎａ３（ＮａＮ３）ｎ）＾＋，（Ｎａ４Ｎ（ＮａＮ３）ｎ）＾＋，（Ｎａ５（ＮａＮ３）ｎ）＾＋，（ＮａＮ３）ｎ）＾＋，（Ｎａｎ）＾＋，（Ｎ３（ＮａＮ３）ｎ）＾－，（Ｎａ（ＮａＮ３）ｎ）＾－，（ＮａＮ３）ｎ）＾－，（Ｎ（ＮａＮ３）ｎ）＾－，提出正负团簇离子形成的可能机理，分析了影响

激光烧蚀叠氮化钠产生的团簇离子及其分布

用飞行时间质谱研究了激光烧蚀叠氮化钠固体产生的正负团簇离子的组成及其分布，产生的团簇系列包括：（Ｎａ（ＮａＮ３）ｎ）＾＋，（Ｎａ３（ＮａＮ３）ｎ）＾＋，（Ｎａ４Ｎ（ＮａＮ３）ｎ）＾＋，（Ｎａ５（ＮａＮ３）ｎ）＾＋，（ＮａＮ３）ｎ）＾＋，（Ｎａｎ）＾＋，（Ｎ３（ＮａＮ３）ｎ）＾－，（Ｎａ（ＮａＮ３）ｎ）＾－，（ＮａＮ３）ｎ）＾－，（Ｎ（ＮａＮ３）ｎ）＾－，提出正负团簇离子形成的可能机理，分析了影响