P. Abdul Azeem

Electronic polarizability and optical basicity properties of oxide glasses through average electronegativity

Abstract The average electronic oxide polarizability ( α o 2− ) and optical basicity ( Λ ) of numerous simple oxides have been estimated on the basis of different properties of oxides: average electronegativity ( χ av ) and energy gap ( E g ). The estimated values are in good agreement with the literature values. Similarly the optical basicity and average electronic polarizability of binary oxides glasses (phosphate, borate, silicate, germanate, tellurite and titanate) have been evaluated on the basis of average electronegativity ( χ av ) only. The performance of the present method is compared with Dimitrov and Komatsu relationships. A good agreement is observed between the computed and literature values.

Absorption and emission spectral studies of Sm3+ and Dy3+ doped alkali fluoroborate glasses

Absorption and photoluminescence spectra of Sm 3 + and Dy 3 + doped alkali fluoroborate glasses of the composition 90.5 B 2 O 3 + 4 AlF + 5 RF + 0.5 LnF 3 (R= Li, Na, K and Ln = Sm, Dy) are reported. On excitation, with 402 nm, the Sm 3 + glasses were found to be orange fluorescent in colour and richness of that colour was high in the Na + glass, compared to Li + and K + glasses. Similarly, on excitation with 398 nm, the Dy 3 + glasses were fluorescent yellow and that colour was richer in the K + glass.

Optical electronegativity, bulk modulus and electronic polarizability of materials

Correlations between the energy gap, optical electronegativity and bulk modulus are given for compound and ternary chalcopyrite semiconductors. Bulk modulus and electronic polarizability values have been evaluated from the optical electronegativity. The estimated values of these parameters are in good agreement with the available experimental data.

Correlation between optical basicity, electronegativity and electronic polarizability for some oxides and oxysalts

A new method for calculating the optical basicity, electronic polarizability and oxygen electronegativity of oxides and oxysalts has been evaluated based on the concept of average electronegativity given by Asokamani and Manjula. The estimated parameters are in good agreement with the Duffy values. The results are also discussed in relation to the nature of bonding. It is suggested that the impurity of average electronegativity in predicting different parameters is well emphasised.

RKRV Potential Energy Curves, Dissociation Energies, γ-Centroids And Franck-Condon Factors Of YO, CrO, BN, ScO, SiO And AlO Molecules

The potential energy curves for the electronic ground states of astrophysically important YO, CrO, BN, ScO, SiO and AlO molecules are constructed techniques using the five-parameter Hulburt-Hirschfelder function. The estimated dissociation energies are 7.235±0.15, 4.337 ± 0.09, 3.917 ± 0.09, 6.899 ± 0.14, 8.181 ± 0.17 and 5.202 ± 0.11 eV for YO, CrO, BN, ScO, SiO and AlO, respectively. The estimated D0 values are in reasonably good agreement with literature values. The r-Centroids and Franck-Condon factors for the bands of B2 Σ+ − X2 Σ+ of YO, B5 Π −X5 Π> of CrO, A3 Π − X3 Π of BN, B2 Σ+ −X2 Σ+ of ScO, E1 Σ+ − X1 Σ+ of SiO and D2 Σ+ − X2 Σ+ and B2 Σ+ −X2 Σ+ of AlO molecules have been determined. The Franck-Condon factors are evaluated by the approximate analytical method of Jarmain and Fraser. The absence of the bands in these systems is explained.

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.

Potential energy curves, dissociation energies and Franck–Condon factors of NI and ScI molecules

Abstract The potential energy curves for the electronic ground states of NI and ScI molecules are constructed by using the RKRV method. The ground state dissociation energies of NI and ScI are determined by curve fitting techniques using the five parameters Hulburt–Hirschfelder function. The estimated dissociation energies are 1.64 and 2.85 eV for NI and ScI, respectively. The estimated dissociation energy values are in good agreement with the literature values. The Franck–Condon factors for the bands b1Σ+–X3Σ− system of NI and B1Π–X1Σ+ system of ScI molecules have been determined using an approximate analytical method of Fraser and Jarmain. The absence of the bands in these systems is explained.

Diurnal and seasonal variabilities in surface ozone and its precursor gases at a semi-arid site Anantapur (14.62°N, 77.65°E, 331 m asl) in India

Measurements of surface ozone and its precursor gases (NOx and CO) have been made at a semi‐arid site Anantapur (14.62°N, 77.65°E, 331 m asl) in tropical Indian region for the period, 2001–2003. NOx and CO levels were the highest during morning and late night hours at this site. Diurnal variations of ozone concentrations varied from 25 ppbv to 50 ppbv and were observed to increase gradually after sunrise, attaining a maximum value by the evening and decreasing gradually thereafter. During monsoon months, the diurnal amplitude of ozone was found to be small (20–25 ppbv). Seasonal variation in ozone showed a pronounced maximum (40–50 ppbv) in the winter and summer. Local pollutants were major contributors to the ozone levels during this period. Ozone shows a yearly mean mixing ratio of about 35.9 ± 8.8 ppbv. The daytime concentration of CO and NOx varied between 200 to 1200 ppbv and 3 to 20 ppbv respectively for the period studied. Annual average mixing ratios of oxides of nitrogen (NOx) and CO were observed to be 3.9±0.6 ppbv and 436±64 ppbv, respectively.

On the equivalence between Clausius–Mossotti and optical electronegativity relations

Abstract The equivalence between Clausius–Mossotti and optical electronegativity relations has been studied. The calculated electronic polarizabilities are in fair agreement with the values obtained from Clausius–Mossotti relations. This work highlights the significance of the interrelation between refractive index and optical electronegativity.

Dissociation energies of astrophysically important MgO, SO, SiN and TiO from spectroscopic data

Abstract The potential energy curves for the electronic ground states of astrophysically important MgO, SO, SiN and TiO molecules are constructed by the RKRV method. The dissociation energies are determined by curve-fitting techniques using the five parameters Hulburt–Hirschfelder function. The estimated dissociation energies are 3.674±0.075, 5.321±0.113, 4.492±0.103 and 6.94±0.16 eV and MgO, SO, SiN and TiO, respectively. The estimated D0 values are in reasonably good agreement with literature values.