Photon-echo profile in the ultrashort time region for pentacene molecules in crystals

Photon-echo behavior in the ultrashort time region is studied for pentacene molecules in p-terphenyl crystals at 1.7 K by means of the accumulated three-pulse echo. We show highly resolved echo spectra with a parameter of time separation and also time behavior of echo intensity as a function of pulse separation measured at various frequencies near the peak position of the absorption line of the S₀–S₁ transition. We demonstrate various features of echo profile in both time and frequency domains, which are dependent on the time region of observation.     

Total synthesis of manoalide and seco-manoalide

The first synthesis of manoalide and seco-manoalide from methyl 7,8-dihydro-β-ionylidene acetate was achieved in high yield by the new method utilizing regiospecific singlet oxygen oxidation of 3-alkenyl-5-trimethylsilylfuran to β-alkenyl-γ-hydroxybutenolide.     

An unusual stereospecific epoxidation with “per-amberlyst 15®”

4-Methyl-4-naphthoquinol and its 5-methyl derivative on treatment with per-Amberlyst 15 are converted to the corresponding cis-2,3-epoxides in high yields. The latter structure was determined by X-ray crystallography.     

A new mechanism of magnetic anisotropy due to π-f exchange in graphite intercalation compound C6Eu

The origin of XY magnetic anisotropy observed in antiferromagnet C₆Eu is studied theoretically. A new mechanism of magnetic anisotropy due to the combined action of the π-f exchange and the spin-orbit interaction is proposed. It is shown that this mechanism overcomes the ordinary mechanism due to the crystal field in the case of a Eu²⁺ ion.     

Time-resolved total internal reflection fluorescence spectroscopy of polymer films

Using total internal reflection, the possibility of a subnanosecond fluorescence spectroscopy for elucidating photophysical and photochemical processes of polymer surface is demonstrated. The thickness which can be studied under the present experimental conditions is of the order of 0.01 μm.     

The band structure and electronic properties of sulphur nitride polymer

A semiempirical calculation of the energy band structure of (SN)_x has been made on a tight-binding model with three p orbitals per atom. An important feature is that the Fermi level crosses two overlapping conduction bands. Measurements are reported of the optical transmission spectrum between 0.2 and 4.0 eV in thin films, the free carrier reflectivity in thick films, and the hydrostatic pressure dependence of the conductivity to 15 kbar. The calculated band structure accounts for experimental results connected with interband transitions (optical absorption) and intraband effects (metallic conductivity, reflectivity, specific heat).     

Photochemische Reaktionen. 98. Mitteilung. Photochemistry of N-Acylimidazoles. III. Rates and Yields of N→C Acyl Migration and of C(α)-C(β) Cleavage of Acyl Side Chains

Relative rates of the photoreactions of 1-( 1 ), 2-( 2 ) and 4(5)-valerylimidazole ( 3 ) as well as the yields of photo-fragmentation product 10 from 1-( 7 ), 2-( 8 ) and 4(5)-stearoylimidazole ( 9 ), respectively, were determined. A reaction path via Norrish Type II fragmentation involving the carbonyl group of 1-acylimidazoles was ruled out.     

Infrared spectrum of acetonitrile: Analysis of Coriolis resonance

The Coriolis resonance between ν₄ and ν₇ in CH₃CN and between ν₁ and ν₅, ν₃ and ν₆, and ν₄ and ν₇ in CD₃CN has been analyzed, applying the technique developed by DiLauro and Mills, to obtain the signs of [$\text{ζ}{}_{\mathrm{r,sa}}{}^{\mathrm{y}}\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$] and the ratio of $\text{?μ}\text{?Q}{}_{\mathrm{r}}$ to $\text{?μ}\text{?Q}{}_{\mathrm{s}}$ for the interacting pairs in CD₃CN. For (ν₄, ν₇) in both CH₃CN and CD₃CN, the sign of [$\text{ζ}{}_{\mathrm{r,sa}}{}^{\mathrm{y}}\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$] is found to be negative as it is also for (ν₁, ν₅) in CD₃CN. For (ν₃, ν₆) the sign of this interaction term is found to be positive. For a given definition of normal coordinates the signs of these interaction terms give the relative signs of $\text{?p}\text{?Q}{}_{\mathrm{r}}$ and $\text{?p}\text{?Q}{}_{\mathrm{sa}}$; our study also gives approximate values for the corresponding ratio [$\text{(}\text{?p}\text{?Q}{}_{\mathrm{r}}\text{)}\text{(}\text{?p}\text{?Q}{}_{\mathrm{sa}}\text{)}$]