Sang Kyu 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

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.

Multidimensional facets of the hydrogen tunneling dynamics of phenol excited in S₁ (ππ*) have been unraveled to give particular S₁ vibronic states strongly coupled or actively decoupled to the O-H tunneling coordinate. Strong mode-dependent variation of the tunneling rate measured with picosecond lasers indicates that tunneling probability is extremely sensitive to low-frequency vibrational modes seemingly orthogonal to the O-H elongation coordinate unless the rate of energ

Soret band lifetimes of the free-base tetraphenylporphine (H(2)TPP) and Cu(ii) tetraphenylporphine (Cu(II)TPP) at 408 nm have been directly measured with femtosecond (fs) resolution using the fluorescence-upconversion technique for the first time, giving tau = 68 +/- 15 and 63 +/- 15 fs, respectively, in benzene solvent.