钾双原子分子23－g－x3∑＋u跃迁扩散带增益特性研究

报道了用单光子激发产生Ｋ２２３ｇ－ｘ３∑＋ｕ跃迁扩散带的实验结果，讨论了此扩散带发射增益特性随温度和缓冲气体压力等条件的变化规律。实验测得了１．２％ｃｍ－１的增益系数。     

A theoretical determination of the dissociation energy of the nitric oxide dimer

Summary Multi-reference CI methods have been applied to determine the dissociation energy and structure of thecis-N₂O₂ molecule. The convergence of the theoretical result has been checked with respect to a systematic expansion of the one-electron basis set and the multi-reference CI wave function. The best calculated value, 13.8 kJ/mol, is in agreement with the experimental value, 12.2 kJ/mol. It has been obtained with an extended ANO-type basis set [6s5p3d2f], including the effect of the basis set superposition error (BSSE) in the geometry optimization, and additional effects, such as the electron correlation of core electrons and relativistic corrections, using the average coupled pair functional (ACPF) approach. The optimal geometry computed at this level was found to be:r(NN)=2.284 Å,r(NO)=1.149 Å, and s5p3d2f] basis set, the BSSE was found to be 2 kJ/mol.     

Inclusion ability of a monothiourea-tethered bis(β-cyclodextrin)

The tail-to-tail monothioureido β-cyclodextrin dimer has been prepared by reacting 6-amino-6-deoxy-β-cyclodextrin with 6-isothiocyanato-6-deoxy-β-cyclodextrin. The inclusion ability of this dimer has been evaluated by UV–visible spectroscopy for substrates of moderate molecular volumes (a wide variety of hydroxylated substrates) and was compared with genuine β-cyclodextrin and randomly methylated β-cyclodextrin. The definition of a complexation index allowed the treatment of these three host molecules on a hierarchical basis: the bis-cyclodextrin appears to be more efficient (average index = 1.17) than the methylated (1.07) or genuine (1.00) monomers. Thus, it seems that the cooperative phenomenon may lead to a general increase of the complexation ability, and not only to an enhanced recognition of specific guests. Surprisingly, this phenomenon is even really effective for the smallest substrates of our study. Such results prompted us to illustrate, on a steric point of view, the possibility of the face-to-face conformation by means of molecular modelling.     

Naphthalenediimide dimers and trimers form self-assembling hydrogen-bonded nanotubes of enhanced stability

Covalent linkage of amino acid-functionalised naphthalenediimides (NDIs) produced a dimer and a trimer that form helical, hydrogen-bonded nanotubes in CHCl₃ solutions and that are more resistant than an analogous monomer to the hydrogen-bond disrupting effects of tetrahydrofuran, methanol and heat.     

Nitro substitution in achiral calamitic liquid crystals

This review examines in some detail the effect of terminal and lateral nitro substitutions in achiral calamitic liquid crystals on their physico-chemical properties. The results of this study are compared with those obtained for other groups, and are rationalized in terms of existing theories.     

Synthesis and characterization of multiblock copolyesters containing poly(dimethylsiloxane) in the soft segments

Synthesis and thermal properties of poly(aliphatic/aromatic-ester) copolymers containing additionally poly(dimethylsiloxane) (PDMS) chains in the soft segments are discussed. A two step method of transesterification and polycondensation from the melt was carried out in a presence of magnesium-titanate catalyst. An aliphatic dimer fatty acid was used as a component of the soft segments while poly(butylene terephthalate) (PBT) constituted the hard blocks. Effectiveness of the incorporation of PDMS into polymer chain was confirmed by the Soxhlet extraction and infrared spectroscopy of an excess of 1,4-butane diol destilled off from the polycondensation reaction. Multiblock copolymers showed microphase separation as determined by differential scanning calorimetry. Incorporation of a small amount of PDMS (up to 14.5 wt.-%) into polymer chain containg low concentration of hard segments of PBT lead to decrease in crystallinity of such copolymers. This may indicate that semicrystalline PBT are dissolved in the amorphous matrix of the soft segments.     

Vibrationally Resolved Inner-Shell Photoexcitation of the Molecular Anion C2−

Carbon 1s core-hole excitation of the molecular anion C₂⁻ has been experimentally studied at high resolution by employing the photon-ion merged-beams technique at a synchrotron light source. The experimental cross section for photo–double-detachment shows a pronounced vibrational structure associated with and core excitations of the C₂⁻ ground level and first excited level, respectively. A detailed Franck-Condon analysis reveals a strong contraction of the C₂⁻ molecular anion by 0.2 Å upon this core photoexcitation. The associated change of the molecule's moment of inertia leads to a noticeable rotational broadening of the observed vibrational spectral features. This broadening is accounted for in the present analysis which provides the spectroscopic parameters of the C₂⁻ and core-excited levels.