• R Gopal

      Articles written in Pramana – Journal of Physics

    • The C (2Π)→X(2Σ+) transition in thermal emission spectra of the diatomic alkaline earth bromides) transition in thermal emission spectra of the diatomic alkaline earth bromides

      M M Joshi R Gopal

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      The extensive thermal emission spectrum attributed to the diatomic bromides of calcium, strontium and barium has been observed in the visible region at temperatures about 2200–2400° C, using a vacuum graphite furnace. Many new bands,viz., 141 in CaBr, 53 in SrBr and 68 in BaBr, have been recorded and classified. The vibrational constants agree with those determined by earlier workers and involved the ground state in each case. The transition C→X apears in each molecule and consists of two equally intense systems,viz., C1→X and C2→X. The general spectroscopic features of the C→X systems of the bromides of the II A sub group of the periodic table have been compared. They exhibit a close structural similarity and furnish a good example of homologous spectra. The system C→X in all these molecules arises from a C2π−X2Σ+ transition where the2π state appears to be intermediate between Hund’s cases (a) and (b).

    • New band systems of NiBr molecule in visible region

      R Gopal M M Joshi

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      Thermal emission spectrum of NiBr molecule excited by vacuum graphite tube furnace revealed the existence of ten new band sub-systems in the region λλ 5540-4720 Å which were attributed toAX,BX,CX andDX transitions. Vibrational analysis was carried out for each of the systems mentioned above.A2 Δ has been suggested as the ground state of NiBr molecule with an electronic interval of about 533 cm−1. Transitions responsible for NiBr spectrum appear to be of the type2π–2Δ and2Δ–2Δ.

    • New band system of MnSe molecule

      K N Uttam R Gopal M M Joshi

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      Thermal emission spectrum of MnSe molecule, excited in high temperature graphite furnace, has been photographed in the spectral region λλ4150–5800 Å at a reciprocal linear dispersion of 7.3 Å/mm. The study reveals the presence of two band systems viz.A–X andB–X in whichB–X is entirely new. While the systemA–X consists of 29 bands, the new systemB–X comprises of 24 single headed and red degraded bands. Vibrational analysis performed suggested that both the systems involve ground state6Σ with a vibrational frequencyωe=361.0 cm−1. Transition responsible for MnSe spectrum appears to be of the type6Σ–6Σ.

      An estimation of the ground state vibrational frequency for MnTe molecule gives rise to its value as 280 cm−1.

    • Laser-induced breakdown spectra of Zn2 molecule in the violet region

      Subhash C Singh K S Ojha R Gopal

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      Laser-induced breakdown spectrum has been recorded in the region of 380–455 nm using second harmonics of Nd:YAG laser, computer-controlled TRIAX 320 M monochromator with a reciprocal linear dispersion 2.64 nm/mm fitted with ICCD detector. The spectrum consists of 108 bands, which are classified into four new subsystems E0u+ (1Σu+) → A1g(3Πg), J0g±\1g(3Σg+) → D1u(1Πu), F1u → A0g±(3Πg) and F1u → A2g(3Πg) along with additional bands of the known system E0u+(1Σu+) → A0g±(3Πg). The molecular constants for these systems have also been determined.

    • Realisation of parallel logic elements and memory latch in a quasiperiodically-driven simple nonlinear circuit


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      We investigate the effect of two aperiodic square waves in a quasiperiodically-driven Murali–Lakshmanan–Chua circuit. It is found that the response of the circuit produces logical output in both strange nonchaotic and chaotic regions. Changing the biasing of the circuit changes the response of the circuit into another kind of logic operation and SR flip flop. Further, we show how this circuit produces two logical elements as its outputs which are complementary to each other. It is also shown that the logical nature of the circuit persists even when experimental noise is present. Thus, we confirm that both the dynamical behaviours, namely strange nonchaos and chaos, can be efficient tools to construct computer architecture.

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