T. V. Ramakrishna Rao

Electron Paramagnetic Resonance and optical absorption spectra of Cr(III) ions in alkali cadmium borosulphate glasses

The Electron Paramagnetic Resonance (EPR) spectrum at 9.205 GHz and at 300 K has been examined for a series of Cr3+ ions doped alkali cadmium borosulphate [R2SO4-CdSO4-B2O3 (RLi,Na,K or Cs)] glasses. The low field EPR spectral resonance lines are attributed to isolated Cr3+ ions where as the high field spectral resonance lines are attributed to exchange coupled pairs of Cr3+ ions. The absorption spectra of Cr3+ ions ions in these glasses show two broad bands characteristic of Cr3+ ions in octahedral symmetry. The bands are slightly shifted to higher wavelength side from Li glass to Cs glass. From the optical spectra the crystal field parameter Dq and the Racah interelectronic repulsion parameters B and C are evaluated. From the EPR and optical data, it is concluded that, the site symmetry around the Cr3+ ions is octahedral and the nature of bonding is predominantly covalent in nature.

Studies on aerosol optical properties over urban and semi-urban environments of Hyderabad and Anantapur

Aerosols in the troposphere exert an important influence on global climate and the environment through scattering, transmission and absorption of radiation as well as acting as nuclei for cloud formation. Atmospheric aerosol particles influence the earths radiation balance directly by scattering of infrared energy and indirectly by modifying the properties of clouds through microphysical processes. The present study addresses visibility, radiative forcing, size distribution and attenuation of aerosols over the period from January to May, 2001 for urban and semi-urban regions of Hyderabad and Anantapur. High aerosol loading has been observed over urban environment compared to semi-urban environment. Aerosol optical depth values increased from January to April and then decreased during May over both urban and semi-urban regions. Over urban region, visibility decreased from January to April and increased during May. Similar trend has been observed over semi-urban region with relatively higher values of visibility. Radiative forcing estimated using aerosol optical depth values increased from January to April and then decreased during the month of May over urban and semi-urban areas. High visibility and low radiative forcing has been noticed over semi-urban area due to less aerosol loading. Wavelength exponent and turbidity coefficient registered high values over urban environment compared to semi-urban environment. Attenuation coefficient showed high values over urban region compared to semi-urban region. It reveals that semi-urban environment receives high solar flux than urban environment. Using 10 channel quartz crystal microbalance, measurements of total mass concentration and mass size distribution of near surface aerosols has been made over semi-urban environment and compared with size distribution derived from inversion methods based on aerosol optical depth variation with wavelength. The sensitivity of constrained linear inversions for inferring columnar aerosol size distributions has been discussed in detail in the paper.

Dissociation energy of Si2 molecule

The true potential energy curves have been constructed for the different electronic states of the Si2 molecule by the methods ofLakshman andRao as well asMorse. The dissociation energy for the ground state of the Si2 molecules has been estimated to be 3.28 eV by the method of curve fitting using the three parameterLippincott potential function. The estimatedDe is in good agreement with the mass spectrometric value 3.25±0.22 eV as well asGaydon’s value 3.35±0.2 eV.

Physical and absorption properties of Nd3+ doped mixed alkali fluoroborophosphate optical glasses

Abstract A new family of three neodymium doped alkali fluoroborophosphate glasses with mixed alkali fluorides as network modifiers have been prepared to study their physical and absorption properties at room temperature. The refractive indices (at 589.3 nm) and densities of these glasses have been measured to examine the effects of the chemical composition on these parameters and also on the other related physical properties. By performing a least square fit analysis, the Judd–Ofelt parameters (Ωλ) have been calculated and are in turn used to evaluate Transition probability (A), radiative lifetime (τR) and branching ratios (βR%) for the fluorescent levels. To understand the lasing efficiency of these materials, the values of the spectroscopic quality factor (Ω4/Ω6) has been evaluated. The radiative characteristics of these mixed alkali fluoroborophosphate glasses have been compared with the results obtained on Nd-glasses possessing the individual alkali fluoroborophosphate glasses as the network modifiers. It is found that Nd-mixed alkali glasses are showing more favorable radiative properties compared with the Nd-glasses having only a single alkali fluorides as the network modifiers.

Dissociation energy of diatomic molecules

Abstract We propose a modified potential energy function that is as easily used as the Hulburt-Hirschfelder (H-H) function. Dissociation energies have been estimated for MgO, CaO, and SrO and other molecules.

The effect of high rotational quantum numbers on Franck-Condon factors

Abstract The effect of high rotational quantum numbers on Franck-Condon factors has been studied for some astrophysically important diatomic molecules by using the criterion of Murthy and Gowda.

Potential energy curves and dissociation energy of the diatomic selenium molecule

The experimental potential energy curves forX13Σg−,X23Σg−,B13Σu−,B23Σu−,C13Σu− andE states of the diatomic selenium molecule have been constructed using the method of Lakshman and Rao and also by Jarmain’s method. The dissociation energy for the ground state of the molecule has been estimated to be 3.31 eV by the method of curve fitting using the electronegativity potential function of Szőke and Baitz. Also the first ionization potential of the Se2 molecule is found to be 8.68 eV.The experimental potential energy curves forX 1 3Σ g − ,X 2 3Σ g − ,B 1 3Σ u − ,B 2 3Σ u − ,C 1 3Σ u − andE states of the diatomic selenium molecule have been constructed using the method of Lakshman and Rao and also by Jarmain’s method. The dissociation energy for the ground state of the molecule has been estimated to be 3.31 eV by the method of curve fitting using the electronegativity potential function of Szőke and Baitz. Also the first ionization potential of the Se2 molecule is found to be 8.68 eV.

Role of electronegativity-evaluation of molecular parameters

The mean electronegativities which are satisfactory approximations for the equalized ones can be brought into close relation with the simplest molecular parameters. The force constants of diatomic molecules AlF, GaF, InF, TlF; SiF, GeF; NF, PF, PF+, AsF and SbF or of simple isolated bonds can be expressed by means of the equalized electronegativities, bond orders, bond strengths and interatomic distances. The performance of the Lennard-Jones parameters has been tested with the potential function proposed bySzőke in calculatingωexe andαe, and found to be excellent. The role of the electronegativity in constructing the ential energy functions proves the validity of the assumption that there is a close connection between electronegativity and the energy relations of the molecules.

Dissociation energy ofP 2 + molecule

The true potential energy curves have been constructed for the different electronic states ofP2+ molecule by the method of Lakshman and Rao. The dissociation energy for the ground state of theP2+ molecule has been estimated to be 4·03 eV by the method of curve fitting using the three-parameter Lippincott potential function. The ionisation potential ofP2 molecule has been estimated as 11·98 eV which is in good agreement with the value given by Gaydon.