T.K. Balasubramanian

On the rotational intensity distribution in the a1Δg → X3Σg− magnetic dipole transition of oxygen molecule

Abstract The relative intensity distribution in the rotational structure of the a1Δg → X3Σg− magnetic dipole transition of molecular oxygen is examined. Use is made of experimental data obtained from the high-resolution (0.02 cm−1) FTS recording of the 0-0 band published by C. Amiot and J. Verges (Canad. J. Phys. 59, 1391–1398 (1981)). Comparison of the experimental and theoretical intensities indicates that rotational linestrength formulas containing purely vibronic transition moments are inadequate and need to be supplemented by two additional parameters of rovibronic origin.

Absorption intensities of zero-phonon single and double transitions in the multipole-induced spectrum of solid hydrogen

Abstract The theory of absorption intensities of some zero-phonon single and double transitions in solid H 2 is discussed. General expressions are developed for the integrated absorption coefficients of (i) the single transitions ( v ′ = v , J ′ = l) ← ( v ″ = 0, J ″ = 0) in solid para -H 2 and ( v ′ = v , J ′ = l + 1) ← ( v ″ = 0, J ″ = 1) in ortho -H 2 interspersed in a matrix of solid para -H 2 , and (ii) the double transition [( v ′ = v 1 , J ′ = l) ← ( v ″ = 0, J ″ = 0)] + S v 2←0 (0) in solid para -H 2 .

Intensity measurement of laser-excited fluorescence in the B3Πu(0+)-X1Σg+ system of diatomic lodine

Abstract Fluorescence was excited in the B3Πu(0+)-X1Σg+ system of diatomic iodine by means of the 5145-A line of an Ar+ laser and the 6328-A line of a HeNe laser. The resulting spectrum was recorded on a SPEX double monochromator and a quantitative measurement of the intensities was carried out. The variation of the electronic transition moment M( R ) with R centroid observed by us shows a behavior similar to what has been reported earlier.

Magnetic dipole and electric quadrupole line strengths for the atomospheric oxygen (b 1Σ g + −X 3Σ g − ) system

Expressions are developed for the magnetic dipole line strengths of rotational transitions in theA-band (0–0 band) of the atmospheric oxygenb1Σg+−X3Σg−) system. The line strengths so derived incorporate effects of spin-uncoupling and orbit-rotation interaction besides, of course, spin-orbit perturbation and are absolute in the sense that the dominant transition moment and intensity parameter which enter the formulae are explicitly expressed in terms of the mutual perturbations characterizing theb andX states. SinceS-branch transitions (necessarily) of electric quadrupole character, have also been detected in theA-band (Brault [11]), we have included a general discussion of branch line strengths for the electric quadrupole intercombination transition1Σ+−2Σ−.

Line strengths in a 3Σ-3Σ quadrupole transition with intermediate coupling : application to line intensities in the quadrupole fundamental band of the oxygen molecule

Abstract Closed form expressions are developed for the intensity factors of the 23 branches resulting from a 3 Σ ± (int)± 3 Σ ± (int) electric quadrupole transition in a diatomic molecule. The rigorous intermediate coupling treatment which includes centrifugal distortion effects results in the occurrence of the U -form and M -form branches which are forbidden in the limit of Hunds case (b) in both the 3 Σ states. The branch intensity factors are used to recalculated the absorption intensities of rovibrational transitions in the quadrupole fundamental band of O 2 . It is shown that depature from the strict case (b) limit moderately affects the intensities of some of the low J transitions.

Multipole moments and polarizabilities of nonpolar diatomic molecules through quantum solvation in solid parahydrogen: The quadrupole moment of N2

It is shown in this paper that from the study of the induced infrared absorption spectra of homonuclear diatomic molecules solvated as impurities in a molecular quantum solid, it is possible to extract information about the rovibrational matrix elements of the multipole moments and polarizability of the embedded molecule. Theoretical expressions are derived for the integrated absorption coefficients of various multipole-field-induced double transitions involving guest-host pairs in a solid para-H(2) matrix. The intensities of some of the quadrupole moment induced transitions involving the N(2)-para-H(2) pair have been measured. From a comparison of the experimental and theoretical intensities, rovibrational matrix elements of the quadrupole moment of N(2) are determined in its ground vibrational state.

Fourier-transform spectroscopic study of the rotational intensity distribution in the first positive B3Πg–A3Σu+ band system of the nitrogen molecule

Abstract In the present work we have studied the rotational intensity distribution in the 0–0, 0–1 and 1–3 bands of the B3Πg–A3Σu+ system of N2 recorded on a Fourier transform spectrometer. The effective Hamiltonian used by Roux et al. (J. Mol. Spectrosc. 97 (1983) 253) for reduction of the experimental line position data to molecular parameters, is found to be adequate in reproducing the observed line intensities. To enhance the accuracy of the theoretical line intensity calculations, it proved necessary to use rotation-dependent Frank–Condon factor. Using the calculated intensities, it was possible to identify certain rotational lines belonging to the weakest branches Q13 and Q31, not reported before.

Intensity mechanisms in the X22Π12-X12Π32 transition of tellurium monohydride

Abstract The intensity mechanisms in a 2 Π 1 2 - 2 Π 3 2 transition are examined in the context of the X 2 2 Π 1 2 -X 1 2 Π 3 2 transition in TeH observed by Fink et al. [J. Mol. Spectrosc.138, 19–28 (1989)]. Such intramultiplet state combinations, though allowed by the magnetic dipole selection rules, are forbidden for the electric dipole mechanism, and yet in TeH the latter choice was made based on the sign of the Λ-doubling parameter q. Our scrutiny of the intensity distribution in the 0-0 band has revealed that branch linestrengths involving a purely vibronic moment are inadequate and need to be supplemented by orbit-rotation corrections. The sizeable Λ-doubling in the X 2 2 Π 1 2 substrate (p ∼ 2 cm−1) allows satisfactory modelling of the intensities on the basis of mixing with a unique perturber 2Σ+ state. The resulting line strength formulas contain the single vibronic moment μ⊥ and the two rovibronic moments Y and Z. Interestingly, the magnitude and even the sign of Z μ ⊥ determined from the intensity fit provide independent evidence negating the magnetic dipole option.

Linestrengths for the electric quadrupole fundamental band of the oxygen molecule with rotation-vibration interaction corrections

Abstract The effect of rotation-vibration interaction on the rovibrational wavefunctions belonging to a 3 Σ electronic state is investigated in the harmonic approximation. The results are used to obtain the Herman-Wallis type corrections to the branch linestrengths of the quadrupole fundamental band of O 2 . The usefulness of the refined linestrength formulas and their limiting forms for Hunds case (b) are discussed.

Rotational linestrengths in 3Δ-3Σ transitions

Transitions involving these levels merit special discussion because of their practical importance in astrophysical applications. In this Note we provide generalized branch linestrength expressions for 3 Δ(int)- 3 Σ(int) and briefly discuss the low J transitions