Raman and Infrared Spectra for All-trans-astaxanthin in Dimethyl Sulfoxide Solvent

The Raman and infrared spectra of all-trans-astaxanthin （AXT） in dimethyl sulfoxide （DMSO） solvent were investigated experimentally and theoretically. Density functional cal-culations of the Raman spectra predict the splitting of the υ1 band into υ1-1 and υ1-2 compo-nents. The absence of splitting in Raman experimental spectra is ascribed to the competition between the two symmetric C=C stretching vibrations of the backbone chain. The υ1 band is very sensitive to the excitation wavelength： resonance excitation stimulates the higher-frequency υ1-2 mode, and off-resonance excitation corresponds to the lower-frequency υ1-1 mode. Analyses of the intramolecular hydrogen bonding between C=O and O-H in the AXT/DMSO system reveal that the C4=O1...H1-O3 and C4＇=O2...H2-O4 bonds are strengthened and weakened, respectively, in the electronically excited state compared with those in the ground state. This result reveals significant variations of the AXT molecular structure in different electronic states.

Efficient Preparation of D2 Molecules in v=2 by Stimulated Raman Pumping

We report the preparation of D2 molecules in v=2 level in molecular beam condition. A single longitudinal mode laser system was used for excitation of D2 from （v=0, j=0） to （v=2, j=0） with the scheme of stimulated Raman pumping. An excitation efficiency of 25.2% has been achieved, which was determined by the scheme of resonance-enhanced multiphoton ion- ization. Dependence of relative excitation efficiency on laser energy has been measured. We found that the increasing rate of excitation efficiency became slower as pulse energy of Stokes laser increase, while the excitation efficiency still increases approximately linearly with pump pulse energies up to 60 mJ. The spectral line shapes of Raman transition was also measured at different laser energies and considerable dynamical Stark effect was observed. A single peak was found on the three dimension surface of relative excitation efficiency, indicating the process occurred in the present study is a process of stimulated Raman pumping instead of stimulated adiabatic Raman passage.

Crossed Molecular Beam Study of H＋CH4 and H＋CD4 Reactions： Vibrationally Excited CH3/CD3 Product Channels

We study the H＋CH4/CD4-＋H2/HD＋CH3/CD3 reactions using the time sliced velocity map ion imaging technique. Ion images of the CH3/CD3 products were measured by the （2＋1） resonance enhanced multi-photon ionization （REMPI） detection method. Besides the CH3/CD3 products in the ground state, ion images of the vibrationally excited CH3/CD3 products were also observed at two collision energies of 0.72 and 1.06 eV. It is shown that the angular distribution of the products CH3/CD3 in vibrationally excited states gradually vary from backward scattering to sideways scattering as the collision energy increases. Compared to the CH3/CD3 products in the ground state, the CH3/CD3 products in vibrationally excited states tend to be more sideways scattered, indicating that larger impact parameters play a more important role in the vibrationally excited product channels.

Efficient Coherent Population Transfer of D2 Molecules by Stark-induced Adiabatic Raman Passage

Preparation of a high flux of hydrogen molecules in a specific vibrationally excited state is the major prerequisite and challenge in scattering experiments that use vibrationally excited hydrogen molecules as the target. The widely used scheme of stimulated Raman pumping suffers from coherent population return which severely limits the excitation efficiency. Re- cently we successfully transferred D2 molecules in the molecular beam from （v=0, J=0） to （v=1, J=0） level, with the scheme of Stark-induced adiabatic Raman passage. As high as 75% of the excitation efficiency was achieved. This excitation technique promise to be a unique tool for crossed beam and beam-surface scattering experiments which aim to reveal the role of vibrational excitation of hydrogen molecules in the chemical reaction.

Excitonic Doppler-Rabi Oscillations in a Moving Organic Slab

It is theoretically shown that excitonic Doppler-Rabi oscillations can occur in an organic slab moving along the axis of a high-Q cavity. Due to the N enhancement of the vacuum Rabi frequency, this effect can be more eas ily observed than that in a moving two-level atom.

Crossed Molecular Beam Study of the F+D2（v=1, j=0） Reaction

The reaction dynamics of the fluorine atom with vibrationally excited D2(v=1, v=0) was investigated using the crossed beam method. The scheme of stimulated Raman pumping was employed for preparation of vibrationally excited D2 molecules. Contribution from the reaction of spin-orbit excited F*(2P1/2) with vibrationally excited D2 was not found. Reaction of spin-orbit ground F(2P3/2) with vibrationally excited D2 was measured and DF products populated in v'=2, 3, 4, 5 were observed. Compared with the vibrationally ground reaction, DF products from the vibrationally excited reaction of F(2P3/2)+D2(v=1, j=0) are rotationally “hotter”. Differential cross sections at four collision energies, ranging from 0.32 kcal/mol to 2.62 kcal/mol, were obtained. Backward scattering dominates for DF products in all vibrational levels at the lowest collision energy of 0.32 kcal/mol. As the collision energy increases, angular distribution of DF products gradually shifts from backward to sideway. The collision-energy dependence of differential cross section of DF(v’=5) at forward direction was also measured. Forward-scattered signal of DF(v'=5) appears at the collision energy of 1.0 kcal/mol, and becomes dominated at 2.62 kcal/mol.

Scheme for Direct Measurement of Wigner Characteristic Function for Motion of a Single Trapped Ion

In this paper, a procedure is proposed for measuring Wigner characteristic function for motion of a single trapped ion. In the scheme, the trapped ion is driven by two laser beams with different frequencies tuned to the first lower and upper vibrational sidebands, respectively. Unlike other previous scheme, our scheme does not require the displacement of the external state before the ion-laser interaction and thus our scheme night be more simple and feasible. The scheme can also be used to prepare the motional Schroedinger cat states and entangled coherent states.

Generation of Arbitrary Pure States for Three-dimensional Motion of a Trapped Ion

In this paper, we propose a scheme for generating an arbitrary three-dimensional pure state of vibrational motion of a trapped ion. Our scheme is based on a sequence of laser pulses, which are tuned to the appropriate vibrational sidebands with respect to the appropriate electronic transition.

Generation of Vibrational Entangled Coherent States of Two Trapped Ions

We propose a scheme for the generation of entangled coherent states for the center-of-mass and relative vibrational modes of two trapped ions. In the scheme the ions are simultaneously illuminated by a single standing-wave laser tuned to the carrier. The scheme allows the production of an entangled coherent states with a considerably high speed as long as a laser field of sufficiently high intensity is available.

Peculiarities of the C2 Swan Band System Intensities in Gas Discharges through CO-Contained Mixtures

The paper discusses the experimental results pointing to the efficient channel of the CO vibrational to the C2 electronic energy-transfer. The radiation spectra of the d3Hg electronic state of C2 molecule are investigated and the relation of their kinetics to a vibrational excitation of CO molecules in the He-CO-O2 plasma is discussed. The changes of CO VED （vibrational energy distribution） were imposed by an application of a laser resonator to the discharge tube under investigation. Strong correlation has been found in experiments between concentrations of vibrationally excited CO molecules and the electronically excited state d31qg of C2 molecule. Modulation of the intensity of lasing oscillation cased marked modulation of the intensity of the emission from d3Hg （Swan bands）. It was found that the vibrational levels 12 〈 w 〈 20 of the CO molecules most effect on the concentration of the C2 （d3flg）. The facts discussed above most probably point to the existence of efficient channel for the VE energy transfer： CO （w） ＋ C2 →CO ＋ C2 （d3II）. The efficiency of this channel increases with the growth of populations of high vibrational levels of CO （X1∑, w）.

飞秒激光二维红外光谱

近年来出现的飞秒激光二维红外(2DIR)光谱技术具有以飞秒时间分辨率测定凝聚相分子动态结构的潜力.时间分辨率取决于飞秒激光的脉冲宽度,分子结构信息存在于二维谱的对角峰和非对角峰中.本文较为全面地论述了2DIR的基本原理,介绍了2DIR的发展历史以及最新动态,特别是近年来2DIR在蛋白质及多肽的结构和动力学方面的代表性研究结果;并以蛋白质酰胺-Ⅰ带为例,着重探讨了一维和二维红外光谱模拟所用的振动激子模型,以及量子化学从头计算、分子动力学模拟在激子模型和光谱模拟中的应用.还简单介绍了偏振光的调控在二维红外光谱学中的用途以及存在的一些实际问题,也介绍了同位素取代,特别是碳-13取代在多肽结构的2DIR表征中的有效性,并分析了水溶液中多肽局部动态结构研究的一个实例.最后,提出了2DIR的一些基础研究方向和应用研究方向以及有待解决的一些技术问题.

Photofragment translational spectroscopy of ICl near 304 and 280 nm: Observation of an intense hot band effect

The photodissociation dynamics of IC1 has been studied near 304 and 280 nm on a simple miniature time of flight (mini-TOF) photofragment translational spectrometer with a short pulse of a weak acceleration field. An intense hot band effect was ob- served. Many small peaks were resolved in each photofragment translational spectrum (PTS). Based on simulations, the principal peaks were assigned not only to the different photodissociation channels (1) I + C1, (2) I + CI*, (3) I* + C1, or (4) I* + CI*, but also to the different chlorine isotopes (35C1 and 37C1). Moreover, some extra peaks showed the existence of an intense hot band effect from vibrationally excited ICI molecules, though only a few percent of ICI molecules remained in the vibrationally excited states in our supersonic molecular beam. Based on the spectra near 304nm, the quantum yield Φ of each channel, the curve crossing, and the branching fraction a from each transition state were determined.