Photoelectron spectroscopy

The energy spectra of photoejected electrons provides a direct method for determining the electronic binding energies in atoms, molecules and solids. The binding energies may be used to identify a particular atom in a molecule or solid and, as well, to indicate from which orbital the electrons were removed. The relative intensities of peaks in the photoelectron spectrum reveal the nature of the chemical bond in a molecule and are a measure of the relative transition probabilities for ionization to a particular state. The effects of autoionization and angular distribution are discussed, and some applications are given.     

High-spin structure of yrast-band in 78Kr

Lifetime of levels up to 22⁺, have been measured in ⁷⁸Kr and an oblate shape is assigned to the ground state using the CSM and the configuration dependent shell correction calculations. Calculations further show that ⁷⁸Kr is highly γ-soft nucleus. The experimental Q _t values coupled with theoretical calculations indicate an oblate shape for ⁷⁸Kr at low spins and triaxial shape at higher spins     

Interaction of NaI with solid water and methanol

The interaction of NaI with amorphous solid water (ASW) and methanol (MeOH) has been investigated with metastable impact electron spectroscopy (MIES), UPS(HeI), and temperature programmed desorption (TPD). We have studied the electron emission from the ionization of the highest-lying states of H(2)O, CH(3)OH, and of 5pI. We have prepared NaI layers on ASW (MeOH) films at about 105 K and annealed them up to about 200 K. Surface segregation of iodide is observed in ASW, as predicted for NaI aqueous solutions. On the other hand, surface segregation is not observed in MeOH, again as predicted for the interaction of NaI with liquid methanol. Electronic properties (ionization potentials, optical band gaps) and water binding energies are reported and are analyzed on the basis of available DFT results for hydrated NaI clusters.     

抗坏血酸有机锗倍半氧化物的合成及抗癌活性研究

通过三氯锗仿与抗坏血酸分子的加成反应,合成了一种新型有机锗倍半氧化物,产物的结构通过元素分析、IR及UV光谱等方法进行了表征．生物活性实验表明合成物对小鼠S-180肿瘤生长具有显著的抑制作用．     

Combinatorial materials research applied to the development of new surface coatings X: a high-throughput electrochemical impedance spectroscopy method for screening organic coatings for corrosion inhibition

The objective of the study was to develop a high-throughput electrochemical impedance spectroscopy (HT-EIS) method for rapid and quantitative evaluation of corrosion protective coatings. A 12-element, spatially addressable electrochemical platform was designed, fabricated, and validated. This platform was interfaced to a commercial EIS instrument through an automated electronic switching unit. The HT-EIS system enables four parallel EIS measurements to be run simultaneously, which significantly reduces characterization time compared to that of serial EIS measurements using a multiplexer. The performance of the HT-EIS system was validated using a series of model systems, including a Randles equivalent circuit, an electrochemical reaction (Ti/K4FeCN6, K3FeCN6), a highly uniform polymer film, and several polymer coatings. The results of the validation studies showed that the HT-EIS system enables a major reduction in characterization time and provides high quality data comparable to data obtained with conventional, single-cell EIS measurement systems.     

Photoswitched singlet energy transfer in a porphyrin-spiropyran dyad.

A photochromic nitrospiropyran moiety (Sp) has been covalently linked to a zinc (PZn) and to a free-base (P(H2)) porphyrin. In the resulting dyads (P(Zn)-Sp(c) and P(H2)-Sp(c)), the porphyrin first excited singlet states are unperturbed by the closed form of the attached spiropyran. Excitation of the spiropyran moiety of either dyad in the near-UV region results in ring opening to a merocyanine form (P-Sp(o)) that absorbs at 600 nm. The open form re-closes thermally in 2-methyltetrahydrofuran with a time constant of 20 s, or following irradiation into the 600 nm band. Excitation of the zinc porphyrin moiety in the merocyanine form of the dyad yields 1PZn-Sp(o). The lifetime of the zinc porphyrin excited state is reduced from its usual value of 1.8 ns to 130 ps by singlet-singlet energy transfer to the merocyanine moiety to give PZn-1Sp(o). The quantum yield of energy transfer is 0.93. Quenching is also observed in the free base dyad, where 1P(H2)-Sp(o) and P(H2)-1Sp(o) exchange singlet excitation energy. This photoswitchable quenching phenomenon provides light-activated control of the porphyrin excited states, and consequently control of any subsequent energy or electron-transfer processes that might be initiated by these excited states in more complex molecular photonic or optoelectronic devices.     

Influence of chirality on phase transitions in ferroelectric liquid crystals

The transition temperatures between various smectic liquid crystal phases are determined as a function of the enantiomeric excess for three different chiralracemic systems (i.e. binary mixtures consisting of a chiral enantiomer and its racemate). It is shown that transitions involving a ferroelectric phase occur in the chiral compounds at higher temperatures compared to their racemates, the temperature shift being proportional to the square of the enantiometric excess. In contrast, for transitions between two non-ferroelectric phases no difference between the chiral and the racemic compounds is found. Various reasons for the experimental behaviour are discussed. A chirality dependence of the transition temperature is also observed for the smectic A-isotropic transition.     

Investigations with infrared spectroscopy on films of the ionic liquid [EMIM]Tf2N

The reflection-absorption infrared (RAIRS) spectra of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM]Tf 2N) are presented as a function of temperature between 114 and 292 K. A comparison is made with the corresponding infrared spectra (obtained with transmission spectroscopy) from bulk [EMIM]Tf 2N. The liquid and amorphous films show rather similar spectra, indicating that the film structure is similar in both cases. On the other hand, these spectra differ considerably from those of crystalline films. Characteristic differences seen between the film and bulk spectra are attributed to the different structures of the respective networks. There are, however, indications that under all studied conditions the cation-anion interaction is between the C-H groups of the [EMIM] ring and the SO 2 groups of the anion.