• G L Bhale

      Articles written in Pramana – Journal of Physics

    • Reinvestigation of the second negative (A2ΠuX2Πg) band system of O2+

      G L Bhale N A Narasimham

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      TheA2Πustate of O2+ was earlier established as an inverted state contrary to previous assumptions. The rotational analysis of a few more bands of theA-X system of O2+ has now been completed. These studies show that the spin-orbit coupling constantA in theA2Πustate gradually varies with the vibrational quantum numberν and is found to be positive forν⩾6. It has also been observed that the spia-rotation interaction is not negligible in theA2Πustate. The spin splitting constantγ is reported for various vibrational levels of this electronic state.

    • Rotational analysis of the 0–9, 0–10 and 0–11 bands of theA2IIu-X2IIg band system of (16O18O)+

      G L Bhale N A Narasimham

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      High-resolution spectra of the 0–9, 0–10 and 0–11 bands of theA2IIuX2IIg system of (16O18O)+ ion have been studied for their rotational structure. This study enables a direct determination of the Λ-doubling parameters of theA2IIu andX2IIg states. The model of ‘pure precession’ explains, though not entirely, the Λ-doubling of theX2IIa state as arising out of its interaction with theB2Σg state. The Λ-doubling in theA2IIu state was found insignificant.

    • Relative photodissociation cross-section of NaCs molecule, using argon ion laser lines

      A Sharma M N Dixit G L Bhale

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      Laser-induced photodissociation of NaCs molecule has been observed when a mixture of Na and Cs metal vapour in a glass cell was irradiated by most of the lines of an argon ion laser. The photodissociation results in the 3P state of Na atoms which is correlated with theF1Σ+ and G1π molecular states of NaCs. Distribution of photofragments over fine structure components 32P3/2 and 32P1/2 of Na has been studied. The ratio of intensity ofD2 line (5890 Å) toD1 line (5896 Å) of Na varies from around 2 at 5145 Å to about 3.5 at 4579 Å. The relative photodissociation cross-section increases monotonically as the wave-length of laser light decreases from 5145 Å to 4579 Å. It is seen that the 4579 Å photon is about 200 times more effective than the 5145 Å photon in causing the photoreaction NaCs + (Ar+ photon) → Na*(3P) + Cs(6S).

    • On the non-BoltzmannA-X emission in Na2 following laser excitation of theB state

      A Sharma G L Bhale M A N Razvi M N Dixit

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      A1Σu+-X1Σg+ emission in Na2 is observed following excitation ofB1πu by various lines of an argon ion laser. The excitation energy ofB1πu is collisionally transferred to the (2)1Σg+ which then radiatively populates theA1Σu+ state. The Na vapour is contained in a stainless steel crossed heat pipe with Ar buffer gas and temperature around 600°C. For all laser lines except 4579 Å, the coarse features ofA-X emission are independent of the laser wavelength. However, at high resolution the finer differences between different laser line excitation are explained. Variousv′-v″ transitions in this emission are identified. Computer simulation is presented to help explain some features of this emission.

    • Three photon resonant ionization in atomic potassium via S, P, D and F series Rydberg states

      A Sharma G L Bhale M A N Razvi

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      Single colour three photon resonant ionization (2 + 1) is observed in atomic potassium vapour in a heat pipe oven using an excimer laser pumped dye laser. Using wavelengths between 570 nm and 603 nm various2S and2D Rydberg states are populated by two photon excitation. Third photon of the same wavelength ionizes the atoms. Rydberg states up ton ⋍ 50 are observed. Electric field as low as 1 V/cm causes extensive Stark mixing of the states. This results in progressively higher three photon ionization signals via the perturbed2P and2F Rydberg states. The three photon ionization process is studied using both linearly and circularly polarized incident light. The experiment shows qualitatively that the2P Rydberg states are perturbed primarily by the2D states in the prescence of an external electric field and to a much smaller extent by2S states. This is also explained theoretically by calculating the Stark mixing coefficients under the Bates and Daamgard (1949) approximation. Implication for a similar effect in other alkali elements is discussed.

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