Photodissociation of Formic Acid at 193 nm: Roaming vs. Transition State Mechanism Detected by Time-Resolved Fourier Transform Infrared Spectroscopy

• Main Authors: Cheng-Jui Tso, 左承叡
• Other Authors: King-Chuen Lin
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/z4ckk3

碩士 === 國立臺灣大學 === 化學研究所 === 107 === In this work, we use time-resolved step-scan Fourier transform infrared spectroscopy to study photolysis mechanism of formic acid at 193 nm. We acquired high-resolution (0.5 cm-1) ro-vibrational spectra of CO produced from photolysis of formic acid in the rage of 1900-2200 cm-1. With the aid of spectral simulation, we can analyze the bi-rotational distribution in v=1 state, and the branching ratio of roaming pathway in v=1 at 0-1 μs is 0.41±0.08. If we fit the vibrational distribution as bimodal, the branching ratio of low-vibrational energy componenet is 0.60±0.03. Comparing with the ion imaging results from Wang’s group and theoredical results from Morokuma’s group, we suggested that the vibrational energy of CO from roaming is higher than that from conventional transition pathway, while the rotational energy of that is lower. According to bi-vibrational distribution,the proportion of the roaming pathway in the reaction of producing CO in the photolysis of formic acid at 193 nm is 0.41±0.02. We succeded in providing a new evidence of roaming phenomena in the photolysis of formic acid.