Photodissociation of Acetaldehyde and Methyl Formate at 308 / 248 nm : Roaming vs. Transition State Mechanism Detected by Time-resolved Fourier Transform Infrared Spectroscopy
Date Issued
2014
Date
2014
Author(s)
Li, Hou-Kuan
Abstract
Since roaming mechanism have been reported in photolysis of formaldehyde at 2004, the papers on this topic have been published mushroomed, such as acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO), methyl formate (HCOOCH3 ) etc. were found to have traces of the roaming mechanism. CO were found to be bi- rotational distribution and with the detection of different rotational states, the proportion contributed by the two mechanism are different. The low-J component of CO are correlated to a very low translational energy. Later, the quasi-classical trajectory calculations also confirmed that the conventional transition state mechanism to form molecular products H2 + CO, CO will have higher angular momentum and with substantial translational energy released.
We use time-resolved Fourier transform infrared spectroscopy to study photolysis reaction of acetaldehyde and methyl formate at 308nm / 248nm. In project of methyl formate, we collaborate with prof. Aquilanti research team in Perugia university in Italy. We obtain the range of 1900-2200cm-1 CO high-resolution (0.25cm-1) spectrum to analyze the internal energy of CO and with the aid of spectral simulation We found that the CO molecule in v = 1 and 2 are bi-rotational distribution. Prof. Aquilanti team perform quasi-classical trajectory calculations, and the experimental results and calculations are quite consistent. In acetaldehyde experiments, we got branching ratio of roaming mechanism in v=1 is 0.10±0.02. Compare to Kable’s LIF results of 0.13, which represents that the time-resolved Fourier transform infrared spectroscopy is a promising method to observe roaming reaction in the internal energy aspect.
Subjects
傅立葉轉換紅外光譜
光分解
乙醛
甲酸甲酯
漫遊機制
Type
thesis
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