An optical transition of 3489 A has been shown to arise from Li using beam foil spectroscopic technique. The mean life of the state emitting this radiation has been measured to be 2.23 ä 0.08 n sec.

The centrifugal distortion analysis of the pure rotational spectrum of pentafluorobenzene in the frequency region of 8 to 18 GHz involvingJ upto 54 has yielded the following rotational and quartic centrifugal distortion constants:$$\begin{gathered} A'' = 1480 \cdot 8665 \pm 0 \cdot 0026 MHz, \tau = - 1 \cdot 751 \pm 0 \cdot 20 kHz, \hfill \\ B'' = 1030 \cdot 0782 \pm 0 \cdot 0025 MHz, \tau _2 = - 0 \cdot 567 \pm 0 \cdot 066 kHz, \hfill \\ C'' = 607 \cdot 5152 \pm 0 \cdot 0026 MHz, \tau _{aaaa} = - 0 \cdot 765 \pm 0 \cdot 068 kHz, \hfill \\ \tau _{bbbb} = - 0 \cdot 612 \pm 0 \cdot 065 kHz, \hfill \\ \tau _{cccc} = - 0 \cdot 547 \pm 0 \cdot 068 kHz. \hfill \\ \end{gathered} $$

The laser Raman spectrum of tere-phthalaldehyde powder has been recorded on a Jobin Yvonhg 2S spectrophotometer with a~100 mW Argon-Ion laser. The infrared spectrum of the solid substance has been recorded on a Perkin-Elmer 621 spectrophotometer in the region 300–4000 cm^-1 using KBr and nujol mull techniques. The observed frequencies have been assigned in terms of the fundamentals, overtones and combinations assumingD_2h point-group symmetry.

Infrared intensity formulae for C₂H₆ and C₂D₆ are derived following the first order approximations. Using the experimental intensities in the intensity equations, the first order coefficients are calculated. They are observed to be negligible compared to the accuracy limits within which the intensities can be measured. Correlating the experimental intensities to the intensity expressions of C₂F₆ and following the zero-order approximations, the bond dipole moment μ and its derivative e are calculated for the C–F bond. Substituting these in the intensity equations of CF₄, transferability of the bond moment parameters is discussed.

A single-crystal neutron-diffraction structural study of PbHAsO₄ in its ferroelectric phase at room temperature (24°C) is presented as part of an investigation of a family of monetites. The crystal structure of PbHAsO₄, and its phase transition mechanism are discussed. Comparison of the crystal structures of PbHPO₄ and PbHAsO₄ reveals that these two ferroelectrics are isomorphous. The role of protons in structural phase transition of PbHAsO₄ is also discussed.

Study of propagation of a spherically converging shock wave has been carried out by Whitham’s method. The variation of shock velocity and pressure along the radius of curvature has been calculated numerically for a number of metals. Attempt has also been made to compare the experimental results of velocity of detonation wave with those reported elsewhere by the application of Whitham’s method. A good agreement between experimental and theoretical results has been obtained in this study.

Dielectric relaxation times (t) have been determined for phenol,o-cresol,m-cresol andp-cresol in solutions ofn-heptane+paraffin oil of varying viscosities. Since, all the four systems contain an -OH group, capable of group rotation, the dielectric absorption was further resolved using Higasi, Koga and Nakamura method in terms oft(1) andt(2). In each case the dielectric relaxation time has been found to be maximum in the neighbourhood of 75%n-heptane+25% p.o. in the mixture. On further increasing the viscosity of the medium, theT values shorten. The results obtained suggest the associative nature of the compounds investigated.

Using suitable factorisation relations and factorisation dependent neutralcurrent parameters of Hung and Sakurai, the neutral current contributions to the parity violating parameters in nuclear force are estimated. Using Cabbibo rotation and Fierz transformation, the charge current contribution is added. It is found that three out of four parity violating parameters can be calculated with respect to their signs and magnitudes. The range of values of the other parameter appears to be small.

For Dynkin labels of weights in 5 and 10 of SU(5), 10 and 16 of SO(10) and 27 ofE, we find it instructive to (a) explōit the Cartan decom position into a nonsemi simple symmetric subalgebra and coset space, (b) introduce a set of annihilation and creation operators, that may act on an invariant 10>, to represent suitably the shift-action and weight-vectors.