Control of branching ratio of reaction products by regulating the orientation of reactive complex in the transition state

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02691
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 32010:Fundamental physical chemistry-related
• Research Institution: Osaka University
• Principal Investigator: Che Dock-Chil 大阪大学, 大学院理学研究科, 講師 (20273732)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 分子の配向制御 / 光解離 / ベクトル相関 / 光吸収の遷移モーメントの方向 / 反応分岐比

Outline of Final Research Achievements

Photodissociation dynamics of isohaloethane at 234 nm was studied by a sliced imaging technique combined with an oriented molecular beam. The speed and angular distributions of the competitive products Br and Cl atoms were determined by analysis of the obtained images. It was found that the Br atoms were generated by direct formation after excitation. In contrast, the Cl atoms may form through long-lived parent molecules after photoexcitation. The branching ratio for Br and Cl atom formation was found to be approximately 1.2, that is, Br atom formation occurred preferentially. A vector correlation study between the laser polarization axis and the direction of the dipole moment revealed a similar tendency for all photofragments, suggesting that the fragments were formed through a common excited state of isohaloethane. The vector correlation was also studied theoretically for comparison with the experimental results.

Free Research Field

反応物理化学

Academic Significance and Societal Importance of the Research Achievements

分子の配向状態を規定した条件下で反応を追跡すれば、反応機構の詳細な解明だけでなく、競争的に生成する生成物の反応分岐比の制御が可能となる。今回、分子の配向状態を規定した条件下で光解離により競争的に生成する生成物の散乱分布を測定した。分子の双極子モーメントの方向とレーザー電場ベクトルとのベクトル相関から分子が光を吸収した後の励起状態へ至る遷移モーメントの方向を実験的に初めて決定することに成功した。本研究手法を用いれば、競争的に生成する生成物のそれぞれの生成機構について明らかにすることが可能であり、長寿命励起状態を経由した光励起の遷移モーメントの方向も決定することが可能である。