Cyclopropenylidene C_3_H_2_ and ethylene oxide C_2_H_4_O molecules are of astronomical importance as their observed lines, distributed throughout the observable microwave region, have a number of pairs having nearly equal frequencies, but different excitation energies and/or belonging to two different species of the molecule. Hence, these molecules may play important role in detecting physical conditions in cosmic objects. Therefore, in order to calculate intensities of the lines, we have investigated transfer of radiation through a cosmic object containing the molecule at a kinetic temperature of 10K. Our results show that some lines of the molecule may be found in absorption against the cosmic 2.7K background.
Einstein A-coefficients for vib-rotational transitions in CS isotopomers, for vibrational quantum number v up to 20, rotational quantum number J up to 140, and {DELTA}v up to 4, are calculated. The change in J is governed by the selection rules {DELTA}J=+/-1. These coefficients play an important role in astronomy, as CS has been observed in a number of astronomical object.
Einstein A-coefficients for the electric dipole transitions in Silicon Dicarbide molecule and its isotopomers between rotational levels of the ground vibrational state up to 51cm^-1^ are calculated. These coefficients are used for computing radiative life times of the levels. The A-coefficients are one of the important input parameters for the radiative transfer calculations.
Einstein A-coefficients for vib-rotational transitions in CO isotopomers, for vibrational quantum number v up to 20, rotational quantum number J up to 140, and {DELTA}v up to 4, are calculated. The change in J is governed by the selection rules {DELTA}J=+/-1. These coefficients play an important role in astronomy, as CO is the most abundant molecule after H_2_, and has been observed in almost all the astronomical objects.
We present new large-scale R-matrix (up to n=4) scattering calculations for the electron collisional excitation of Cl-like NiXII. We used the intermediate-coupling frame transformation method. We compare predicted and observed line intensities using laboratory and solar spectra, finding good agreement for all the main soft X-ray lines. With the exception of the three strongest transitions, large discrepancies with previous estimates are found, especially for the decays from the lowest 3s2 3p4 3d levels. This includes the forbidden UV lines. The atomic data for the n = 4 levels are the first to be calculated. We revise previous experimental energies, and suggest several new identifications. We point out the uncertainty in the wavelength of the 3s2 3p5 2P1/2 3s2 3p4 3d 2D3/2 transition, which is important for density diagnostics.
Effective collision strengths are presented for transitions from the 16 states of the 3d(5) configuration to the higher lying states belonging to the 3d(4)4s and 3d(4)4p configurations of Fe IV. Collision strength calculations performed with 108 coupled states (in LS-coupling) using the parallel R-matrix code PRMAT are used to determine the effective collision strengths by averaging them over a Maxwellian temperature distribution for the electrons. Each of the LS term level is assigned a label ranging from 1 to 108. Note; 1 to 16 refers to states associated with the 3d(5) configuration; 6S, 4G, 4P, 4D, 2I, 2D3, 2F2, 4F, 2H, 2G2, 2F1, 2S, 2D2, 2G, 2P and 2D1. Effective collision strengths data for 11 temperatures are presented (non-zero values) for electron temperatures ranging from ~2000 to 1000000K (i.e. log10(T)=3.3 to log10(T)=6.0).
We present our calculated data including energy levels and lifetimes (in table1), radiative rates, oscillator strengths and line strengths (in table2), collision strengths (in table3), and effective collision strengths (in table4) for all the transitions among 36 fine-structure levels from n<=6 configurations in H-like ions with 13<=Z<=42.
Collision strengths for electron impact excitation of fine-structure levels in sulfur-like Fe XI are calculated in a semirelativistic R-matrix approach. The 38 fine-structure levels arising from the 20 LS states 3s^2^3p^4^ ^3^P, ^1^D, ^1^S; 3s3p^5^ ^3^P^0^, ^1^P^0^; 3s^2^3p^3^(^4^S^0^)3d ^3^D^0^, 3s^2^3p^3^(^2^P^0^)3d ^1,3^P^0^, ^1,3^D^0^, ^1,3^F^0^, 3s^2^3p^3^(^2^D^0^)3d ^1,3^S^0^, ^1,3^P^0^, ^1,3^D^0^, ^1,3^F^0^ are included in our calculation. The target levels are represented by configuration interaction wave functions. The relativistic effects are considered in the Breit-Pauli approximation by including one-body mass correction, Darwin term, and spin-orbit terms in the scattering equations. Collision strengths for transitions from the 3s^2^3p^4^ ^3^P_2,1,0_ levels to the fine-structure levels of the 3s^2^3p^3^3d configuration are compared with the distorted-wave results of Bhatia & Doschek (1996) at 8.0, 16.0, 24.0 ryd. There are some significant discrepancies between the two calculations, mostly caused by the difference in target wave functions. The collision strengths are integrated over a Maxwellian distribution of electron energies to obtain effective collision strengths over the temperature range from 5x10^5^ to 5x10^6^ K.
Energy levels, radiative rates, collision strengths, and effective collision strengths for all transitions up to and including the n=5 levels of Al XIII have been computed in the jj coupling scheme including relativistic effects. All partial waves with angular momentum J<=60 have been included, and resonances have been resolved in a fine energy grid in the threshold region. Collision strengths are tabulated at energies above thresholds in the range 170.0<=E<=300.0Ryd, and results for effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, are tabulated over a wide temperature range of 4.4<=logT_e_<=6.8K. The importance of including relativistic effects in a calculation is disc ussed in comparison with the earlier available non-relativistic results.
Emission from Ar III is seen in planetary nebulae, in H II regions, and from laboratory plasmas. The analysis of such spectra requires accurate electron impact excitation data. The aim of this work is to improve the electron impact excitation data available for Ar^2+^, for application in studies of planetary nebulae and laboratory plasma spectra. The effects of the new data on diagnostic line ratios are also studied. Electron-impact excitation collision strengths have been calculated using the R-Matrix Intermediate-Coupling Frame-Transformation method and the R-Matrix Breit-Pauli method. Excitation cross sections are calculated between all levels of the configurations 3s^2^3p^4^, 3s3p^5^, 3p^6^, 3p^5^3d, and 3s^2^3p^3^nl (3d<=nl<=5s). Maxwellian effective collision strengths are generated from the collision strength data.
