Ju-Long Sun

Photodissociation dynamics of the S2 state of CH3ONO: State distributions and alignment effects of the NO (X2Π) photofragment

The photodissociation dynamics of methyl nitrite (CH3ONO) was studied using 266 nm laser photolysis, and NO photofragments X 2∏ ν″=0,1,2,3) were probed by single photon laser-induced fluorescence spectroscopy. The ground vibrational state of the NO was found to be most populated, and the rotational distributions of each vibrational level were quite hot. The alignment A0(2) between the electronic transition dipole moment involved in the absorption of the parent molecule and the rotational angular momentum J of the photofragment NO (v″=0) was measured. Polarization experiments showed that the rotational angular momentum of NO was aligned perpendicularly to the transition moment of the parent molecule. The negative A0(2) values and a preferential population of the ∏− doublet state revealed that the dissociation process has some characteristics of in-plane dissociation.

Photodissociation of nitrobenzene at 266 nm: Experimental and theoretical approach

The 266 nm photodissociation of gaseous nitrobenzene has been studied by monitoring the NO X 2Π product using the single-photon laser-induced fluorescence technique. The rotational population and internal energy distributions of fragment NO product were determined. In the experiment, we only observed the rotational state distributions of the NO fragment for v″=0. The rotational state distributions of the nascent NO photofragment can be characterized by a Boltzmann temperature of 3300±300 K. Ab initio calculations were performed to characterize the transition state and to determine the barrier height for the rearrangement of nitrobenzene to phenylnitrite. A clear photodissociation picture has been proposed theoretically.

Photolysis of o-nitrobenzaldehyde in the gas phase: a new OH* formation channel.

Photolysis of gaseous o-nitrobenzaldehyde (o-NBA) with selected different excitation wavelengths (355-400 nm) is investigated, and the nascent OH radical is detected by the single-photon laser-induced fluorescence (LIF) technique. The relative quantum yield and rotational excitation of OH formation are found to be dependent on the excitation energy. The distributions of rotational, spin-orbit, and Lambda-doublet states are obtained at 355-400 nm by analyzing the experimental data. The OH radicals are found to be vibrationally cold at all photolysis wavelengths. The spin-orbit and Lambda-doublet states have nonstatistical distributions. To understand the dissociative process involved in the OH-generating channel, DFT calculations are performed. Based on both experimental and theoretical results, possible photolysis channels of o-NBA leading to the OH fragment are proposed and discussed.

Photodissociation Dynamics of Nitromethane and Nitroethane at 266 nm

Measurements of the nascent OH product from photodissociation of gaseous nitromethane and nitroethane at 266 nm were performed using the single-photon laser induced fluorescence technique. The OH fragment is found to be vibrationally cold for both systems. The rotational state distribution of nitromethane are Boltzmann, with rotational temperature of T-rot=2045 +/- 150 and 1923 +/- 150 K for both (2)Pi(3/2) and (2)Pi(1/2) states, respectively. For nitroethane, the rotational state distribution shows none Boltzmann and cannot be well characterized by a rotational temperature, which indicates the different mechanisms in producing OH radicals from photodissociation of nitromethane and nitroethane. The rotational energy is calculated as 14.36 +/- 0.8 and 4.98 +/- 0.8 kJ/mol for nitromethane and nitroethane, respectively. A preferential population of the low spin-orbit component ((2)Pi(3/2)) is observed for both nitromethane and nitroethane. The dominant population of Pi(+) state in two Lambda-doublet states is also observed for both nitromethane and nitroethane, which indicates that the unpaired pi lobe of the OH fragment is parallel to the plane of rotation.

Internal-state distribution and polarization in nascent NO X2Π from the photodissociation of C6H5NO

Abstract The 266 nm photodissociation of gaseous C6H5NO has been studied by monitoring the nascent NO ( X 2 Π v″=0–3 ) product using the single-photon laser-induced fluorescence technique. The rotational-state distributions of the nascent NO photofragment have been measured and can be characterized by Bolzmann temperatures. The vibrational-state and Λ-doublet populations were also determined. Energy disposal into the internal degrees of freedom of NO ( X 2 Π ) photofragment is about 18% of the total available energy. Some planarity in the fragmentation process was observed.

A density function theory study on the properties and decomposition of CF3OF

The density function theory was used to calculate the potential energy surface for the decomposition of CF3OF. The geometries, vibrational frequencies and energies of all stationary points were obtained. The calculated harmonic frequencies agreed well with the experimental ones. Three decomposition channels of CF3OF were studied. The calculated reaction enthalpy (29.85 kcal/mol) of the elimination reaction CF3OF --> CF2O + F-2 was in good agreement with the experimental value (27.7 kcal/mol). The O-F bond of CF3OF is broken easily by comparing the energies, while the decomposition channel to yield the CF30 and F radicals is the main reaction path