Sang‐Gyu Kim

Abstract The surface‐enhanced Raman (SER) spectra of aromatic amino acids ( L ‐phenylalanine, L ‐tyrosine and tryptophan) and their glycyl dipeptides (glycyl‐ L ‐phenylalanine, glycyl‐ L ‐tyrosine and glycyl‐ L ‐tryptophan) adsorbed on Ag colloidal particles have been obtained. The surface‐enhanced and ordinary Raman spectra show satisfactory correlations. The most prominent features in the SER spectra of all compounds are the strongly enhanced peaks at about 930 and 1390 cm −1 due to the CCOO

When a reaction involving two equivalent bonds has sufficient energy to break both of them, it can proceed by either a concerted or a stepwise mechanism. For Norrish type-I and other reactions, this issue has been controversial since direct time resolution of the individual C–C cleavage events was not possible. Here, for the elementary α-cleavage of acetone, we report on the femtosecond resolution of the intermediates using mass spectrometry. The results show the nonconcertedness of the reaction

Abstract Surface‐enhanced Raman scattering (SERS) of adenine, adenosine, 2′‐deoxyadenosine, 5′‐dAMP, 5′‐rAMP, 5′‐rADP and 5′‐rATP adsorbed on aqueous Ag sol has been investigated. A shift of the adenine ring breathing mode from 746 to 735 cm −1 with increasing adenine concentration is interpreted as reflecting the reorientation of adenine on the Ag surface. Such a shift is not observed for adenosine, 2′‐deoxyadenosine and 5′‐dAMP. SERS spectra of 5′‐rAMP, 5′‐rADP and 5′‐rATP can be obtained eith

Rate constants for the unimolecular dissociation of ketene (CH2CO) and deuterated ketene (CD2CO) have been measured at the threshold for the production of CH2 (X̃ 3B1) or CD2 (X̃ 3B1) and CO (X̃ 1Σ+) by photofragmentation in a cold jet. The rate constant increases in a stepwise manner as energy increases. This is in accord with the long-standing premise that the rate of a unimolecular reaction is controlled by flux through quantized transition-state thresholds at each energy level for vibrationa

The rotational distributions of CO products from the dissociation of ketene at photolysis energies 10 cm−1 below, 56, 110, 200, 325, 425, 1107, 1435, 1720, and 2500 cm−1 above the singlet threshold (30 116.2 cm−1 ), are measured in a supersonic free jet of ketene. The CO(v″=0) rotational distributions at 56, 110, 200, 325, and 425 cm−1 are bimodal. The peaks at low J′s, which are due to CO from the singlet channel, show that the product rotational distribution of CO product from ketene dissociat

Femtosecond chemical activation of reactions at very high thermal energies, much above the bond energy, is developed in this report. We address the concept of nonstatistical dynamics at such high energies. The approach offers a new direction for probing the dynamics of reactions in their ground state with unique activation, collision-free, and temporally and spatially defined.

The S-D bond dissociation dynamics of thiophenol-d1 (C6H5SD) pumped at 266, 243, and 224 nm are examined using the velocity map ion imaging technique. At both 266 and 243 nm, distinct peaks associated with X and A states of the phenylthiyl radical (C6H5S*) are observed in the D+ image at high and low kinetic energy regions, respectively. The partitioning of the available energy into the vibrational energy of the phenylthiyl radical is found to be enhanced much more strongly at 266 nm compared to

Looking into temporal dynamics of the reactive flux that is precisely located at the well-characterized conical intersection has been one of chemists’ longstanding goals. We report here real-time nonadiabatic bifurcation dynamics in the S–CH 3 bond predissociation of thioanisole (C 6 H 5 SCH 3 ) in the first electronically excited state (S 1 ). It is found that two distinct adiabatic and nonadiabatic reaction pathways are activated simultaneously only when the vibronic state near the first conic

Surface crossing of bound (S 1, ππ*) and continuum (S 2, πσ*) states has been observed in the ultrafast S–D bond dissociation reaction of thiophenol- d 1 . It is manifested by an unanticipated variation of fragment angular distribution as a function of the excitation energy. The anisotropy parameter (β) of +0.25 at the S 1 origin decreases to −0.60 at ∼600 cm –1 above the S 1 zero-point level, giving a broad peak in β with a bandwidth of ∼200 cm –1 . The peak in β is ascribed to the in-plane S-D

The one-photon mass-analyzed threshold ionization (MATI) spectroscopy of bis(η 6 -benzene)chromium is reported. The adiabatic ionization energy is accurately measured to be 44 087 ± 5 cm -1 (5.4661 ± 0.0006 eV). The Cr−benzene stretching vibrational mode in the ion with a fundamental frequency of 264 cm -1 is found to be optically active. The MATI spectra of bis(η 6 -benzene)chromium·Ar and bis(η 6 -benzene)chromium·benzene clusters are also reported to give ionization potentials of 43 941 ± 5 c

Semiconductor–metal hybrid nanostructures are one of the best model catalysts for understanding photocatalytic hydrogen generation. To investigate the optimal structure of metal cocatalysts, metal–CdSe–metal nanodumbbells were synthesized with three distinct sets of metal tips, Pt–CdSe–Pt, Au–CdSe–Au, and Au–CdSe–Pt. Photoelectrochemical responses and transient absorption spectra showed that the competition between the charge recombination at the metal–CdSe interface and the water reduction on t