• H C MANJUNATHA

      Articles written in Pramana – Journal of Physics

    • Gamma dosimetric parameters in some skeletal muscle relaxants

      H C MANJUNATHA

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      We have studied the attenuation of gamma radiation of energy ranging from 84 keV to 1330 keV $(^{170}Tm, ^{22}Na, ^{137}Cs, and ^{60}Co)$ in some commonly used skeletal muscle relaxants such as tubocurarine chloride, gallamine triethiodide, pancuronium bromide, suxamethonium bromide and mephenesin. The mass attenuation coefficient is measured from the attenuation experiment. In the present work, we have also proposed the direct relation between mass attenuation coefficient $(\mu/\rho)$ and mass energy absorption coefficient $(\mu_{en}/\rho)$ based on the nonlinear fitting procedure. The gamma dosimetric parameters such as mass energy absorption coefficient $(\mu_{en}/\rho)$, effective atomic number $\rm{(Z_eff )}$, effective electron density $(N_\rm{el})$, specific $\gamma$-ray constant, air kerma strength and dose rate are evaluated from the measured mass attentuation coefficient. These measured gamma dosimetric parameters are compared with the theoretical values. The measured values agree with the theoretical values. The studied gamma dosimetric values for the relaxants are useful in medical physics and radiation medicine.

    • Parametrisation of the experimental fusion–fission cross-sections

      H C MANJUNATHA N SOWMYA

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      We have presented non-linear analytical formula for fusion–fission cross-sections. This is achieved by analysing many fusion–fission experiments of the compound nuclei of atomic number range $23 \leq Z \leq 146$ available in literature. Our parametrised formula can reproduce the fusion–fission cross-sections which agree well with the experiments. Our parametrisations depend on the charges and masses of the compound nuclei and fission fragments only. These results can be used as a guideline for estimating the fusion–fission cross-sections in those cases where measurements do not exist and also for studying new nuclei which are not yet explored.

    • Systematic study of the $\alpha$ decay properties of actinides

      G R SRIDHARA H C MANJUNATHA K N SRIDHAR H B RAMALINGAM

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      This work analyses the $\alpha$ decay properties of actinides. Geiger–Nuttall plots are presented for actinides. We have studied the competition between $\alpha$ decay and spontaneous fission and have identified the dominant decay mode. The results have been compared with experiments and they agree well with those of the experiments.

    • Empirical formula for beta-particle-induced bremsstrahlung yields

      H C MANJUNATHA

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      We have measured the $\beta$-particle-induced bremsstrahlung energy yield and photon yield in the energy range 0.1668–2.274 MeV using beta sources such as $^{35}$S (0.1668), $^{99}$Tc (0.293), $^{147}$Pm (0.225), $^{90}$Sr(0.5462), $^{204}$Tl (0.76), $^{91}$Y (1.5), $^{32}$P (1.71) and $^{90}$Y (2.274 MeV) in thick targets of atomic number range $13< Z< 83$. We have used a NaI(Tl) detector to measure the bremsstrahlung radiations. Based on the experimental results, we have constructed a semiempirical formula for $\beta$-particle-induced bremsstrahlung energy yield and photon yield. This formula produces bremsstrahlung energy yield and photon yield in the energy range 0.1668 MeV$ < E_{\rm{max}} < 2.274$ MeV for thick targets within the atomic number range $13 < Z < 83$. The values produced by the present formula are compared with the experiments.

    • Decay of dinuclear systems formed from dubnium

      A M NAGARAJA H C MANJUNATHA N SOWMYA P S DAMODARA GUPTA S ALFRED CECIL RAJ

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      The radioactivity of the superheavy nuclei ${}^{250−275}$Db is studied and presented using the Coulomb and proximity potentials. The half-lives corresponding to different decay modes such as α, cluster decay (${}^{12}$C, ${}^{14}$N,${}^{18,20}$O, ${}^{23}$F, ${}^{20}$Ne, ${}^{34}$S, ${}^{28}$Mg and ${}^{40}$Ca) and spontaneous fission in the superheavy nuclei ${}^{250−275}$Db are studied. The studied half-lives are compared with the available experiments. The decay modes and the branching ratios of isotopes of dubnium are presented. The isotopes of dubnium, ${}^{254−263}$Db, are identified as α emitters, whereas isotopes such as ${}^{250−253}$Db and ${}^{264−275}$Db are identified as having spontaneous fission. The identified alpha emitting isotopes of dubnium have decay energies from 6 MeV to 10 MeV and half-lives 1 ms to 100 s. The possible projectile–target combinations to synthesise the superheavy nuclei ${}^{253−263}$Db were predicted. The fusion of spherical projectile and target yields larger evaporation residue cross-sections.

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