Optical properties of the semiconductor 7, 7′, 8, 8′, tetracyanoquinodimethane (TCNQ)

Summary The reflectivity and absorption spectra of 7, 7′, 8, 8′ tetracyanoquinodimethane thin films, in the visible and near-ultraviolet range, have been measured. Samples have been grown and characterized by means of elemental microanalysis and differential scanning calorimetry (DSC) in order to obtain the purity degree. The experimental optical spectra are interpreted on the basis of a calculation of the electronic molecular energy levels by the complete neglect of differential-overlap method in a new parametrization scheme. Work partially supported by the Ministero della Pubblica Istruzione through the G.N.S.M.     

Vibrational spectra of styrene-H8, -D3, -D5, and -D8

Infrared and Raman spectra of C₆H₅CHCH₂, C₆H₅CDCD₂, C₆D₅CHCH₂, and C₆D₅CDCD₂ liquids are analyzed to assign their fundamental vibrations.     

Editorial board page for “Spectroscopy Letters”, Volume 8, Number 8

This is a scanned image of the original Editorial Board page(s) for this issue.     

Fluorescences of styrene-H8, -D3, -D5, and -D8 in polycrystalline methylcyclohexane at 77 K

From analyses of 77 K fluorescence and fluorescence excitation spectra of styrene and three deuterium substituted isomers, it is concluded that the S₀ ? S₁ transition is of a ¹A₁ ? ¹A₁ nature (in C_2v).     

Neutron diffraction study of RMn4Al8 (R = Nd,Dy, Ho,Er), ErCr4Al8 and ErCu4Al8

Neutron powder diffraction has been used to investigate the magnetic order in a series of RMn₄Al₈ (space group I₄/mmm) compounds with R = (Nd, Dy, Ho and Er). For compounds with Mn, no magnetic order was detected down to 1.6 K, whilst for the compound ErCr₄Al₈, two very weak magnetic reflections were observed at 1.6 K. The observed magnetic peaks cannot be indexed on the tetragonal unit cell, indicating a possible incommensurate magnetic structure. For ErCu₄Al₈, a type 1 antiferromagnetic structure is observed. The magnitude and temperature dependence of the Er³⁺ magnetic moment can be adequately modelled by a combined isotropic exchange and tetragonal crystal field Hamiltonian within the Mean Field Approximation.     

A study of the second excited state of8Be by the10B(d,α2)8Be-reaction

The second excited state of⁸Be has been studied by analysis of the coincidence spectra of the reaction¹⁰B(d, α)2α forE _d =1.0-2.0 MeV. The excitation energy was found to be 12.0±0.4 MeV, and the reduced width 0.85±0.12 MeV. Differential crosssections of the (d, α ₂)-reaction were deduced.     

Kl3 from factors and (8, 8) model of chiral symmetry breaking

K_l3 form factors are calculated in the single particle approximation to the spectral functions. The so-called sigma terms and current divergences are calculated in the (8, 8) model of chiral symmetry breaking. Comparison with the experimental results and the (3,3¹) + (3¹, 3) model is made. It is concluded that it is not possible to rule out the (8, 8) model in favor of the (3,3¹) + (3¹) + (3¹, 3) model at present.     

First observation of the (4He,8B) reaction

The (⁴He,⁸B) reaction on²⁷Al and⁶⁶Zn targets has been studied atE _α=109MeV, the first observation of this reaction. Five groups appear in the first 4 MeV of excitation in the²³Ne spectrum, with laboratory differential cross sections ranging from 35 to 384 nb/sr atθ _lab=8⁰. Individual levels in⁶²Co were not resolved in the exposure on the⁶⁶Zn target. However,⁸B events were observed which are tentatively attributed to the⁶⁶Zn(α,⁸B)⁶²Co reaction, since contributions from plausible target contaminants can be eliminated on the basis ofQ value. The observed yield at 8⁰ indicates a laboratory cross section of 540 nb/sr summed over the first 4.6 MeV of excitation in⁶²Co.     

Normal co-ordinate analysis of 1, 8-dibromooctane

The organic compound 1,8-dibromooctane (1,8-DBO) exists in liquid phase at ambient temperatures and has versatile synthetic applications. In its liquid phase 1,8-DBO has been expected to exist in four most probable conformations, with all its carbon atoms in the same plane, having symmetries C _2h , C _i , C ₂ and C ₁ . In the present study a detailed vibrational analysis in terms of assignment of Fourier transform infrared (FT-IR) and Raman bands of this molecule using normal co-ordinate calculations has been done. A systematic set of symmetry co-ordinates has been constructed for this molecule and normal co-ordinate analysis is carried out using the computer program MOLVIB. The force-field transferred from already studied lower chain bromo-alkanes is subjected to refinement so as to fit the observed infrared and Raman frequencies with those of calculated ones. The potential energy distribution (PED) has also been calculated for each mode of vibration of the molecule for the assumed conformations.