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제126회 대한화학회 학술발표회 및 총회 Ultrafast dynamics study of organosulfur molecule using x-ray absorption spectroscopy at PAL-XFEL

2020년 9월 17일 11시 47분 03초
PHYS.P-237 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
10월 21일(수) 17:30~18:00
Physical Chemistry
저자 및
Rory Ma, Jae Hyuk Lee*
PAL-XFEL, Pohang Accelerator Laboratory, Korea
Time-resolved X-ray Absorption Spectroscopy (TR-XAS) is powerful tool to probe time-evolving electronic and molecular structural dynamics in ultra-short timescale. For example, in S K-edge, it is sensitive to both the charge and the character of the low-lying valence orbitals in S atom. In this work, we investigated the early stage dynamics in proton transfer reaction of 2-Thiopyridone (2TP) in femtosecond time domain. 2TP complex is widely used in general chemical synthesis, antimicrobial and antifungal uses [1,2]. 2TP has a tautomer form, 2-mercaptopyridine (2MP) by proton transfer between S and C. Photoexcitation of 2TP which leads to the formation of 2MP was studied with 70-ps temporal resolution in our group using synchrotron, Advanced light source (ALS) [3]. We searched the early stage dynamics of photoreaction of 2TP by S K-edge TR-XAS at PAL-XFEL. PAL-XFEL is unique facility for tender X-ray (2~5 keV) TR-XAS in intensity. 2TP was excited by 400-nm fs laser pulse and 2.48 keV (S K-edge) XFEL was used as probe. Proton transfer reaction of 2TP was tracked with 150 fs temporal resolution. Our measurement shows the key spectral changes from 2TP to 2MP in several hundreds of ps time range which we’ve already found our previous measurement [3], and we picked up another short-lived intermediate at sub-ps time range. We estimate the short-lived intermediate as highly excited 2TP and the highly excited 2TP was relaxed to triplet state of 2TP within 1 ps. To support experiment result, we also calculate theoretical XAS spectra using time-dependent density functional theory. References [1] J. Am. Chem. Soc. 72, 4362–4364 (1950). [2] Selective Toxicity: The Physico-Chemical Basis of Therapy, 7th ed. (Chapman and Hall, London, 1985). [3] Struct. Dyn. 4, 044021 (2017)