• Volume 18, Issue 4

April 1982,   pages  295-383

• Excited atomic state of Li

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.

• Centrifugal distortion constants of pentafluorobenzene from its pure rotation spectrum

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:$$\begin{gathered} A'' = 1480 \cdot 8665 \pm 0 \cdot 0026 MHz, \tau = - 1 \cdot 751 \pm 0 \cdot 20 kHz, \hfill \\ B'' = 1030 \cdot 0782 \pm 0 \cdot 0025 MHz, \tau _2 = - 0 \cdot 567 \pm 0 \cdot 066 kHz, \hfill \\ C'' = 607 \cdot 5152 \pm 0 \cdot 0026 MHz, \tau _{aaaa} = - 0 \cdot 765 \pm 0 \cdot 068 kHz, \hfill \\ \tau _{bbbb} = - 0 \cdot 612 \pm 0 \cdot 065 kHz, \hfill \\ \tau _{cccc} = - 0 \cdot 547 \pm 0 \cdot 068 kHz. \hfill \\ \end{gathered}$$

• Raman and infrared spectra of tere-phthalaldehyde

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 assumingD2h point-group symmetry.

• Infrared intensity analysis of molecules C2H6, C2D6, C2F6 and CF4 zero and first order approximations

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 neutron diffraction study of ferroelectric PbHAsO4 at room temperature

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.

• Converging shock waves in metals

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.

• Relaxation behaviour of phenol and cresols in highly viscous media

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.

• Estimation of parameters in parity-violating nuclear force using single-Z-boson factorisation relations

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.

• Weights of elementary representations in SU(5)-SO(10)-E6 chain

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&gt;, to represent suitably the shift-action and weight-vectors.

• # Pramana – Journal of Physics

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