• 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.

    • Search for a viable nucleus–nucleus potential in heavy-ion nuclear reactions

      T NANDI D K SWAMI P S DAMODARA GUPTA YASH KUMAR S CHAKRABORTY H C MANJUNATHA

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      We have constructed empirical formulae for the fusion and interaction barriers using a large number of experimental values chosen randomly from the literature available till date. The obtained fusion barriers have been compared with different model predictions based on the proximity, Woods–Saxon and double folding potentials along with several empirical formulas, time-dependent Hartree–Fock theories and experimental results. The comparison allows us to find the best model, which is nothing but the present empirical formula only. Most remarkably, the fusion barrier and radius show excellent consonance with the experimental findings for the reactions meant for the synthesis of super heavy elements also. Furthermore, it is seen that substitution of the predicted fusion barrier and radius in classic Wong formula (Wong,Phys. Rev. Lett. $31$:766 (1973) for the total fusion cross-sections agrees very well with the experiments. Similarly, current interaction barrier predictions have also been compared well with a few experimental results available and Bass potential model meant for the interaction barrier predictions. Importantly, the present formulae for the fusion as well as interaction barrier will have practical implications incarrying out physics research near the Coulomb barrier energies. Furthermore, the present fusion barrier and radius provide us with a good nucleus–nucleus potential which is useful for numerous theoretical applications.

    • Heavy ion fusion with lead and bismuth targets

      P S DAMODARA GUPTA H C MANJUNATHA N SOWMYA L SEENAPPA N MANJUNATHA T GANESH

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      The cold fusion reactions with lead and bismuth as targets were used in the synthesis of superheavy elements (SHE) with mass number up to 113. Researchers ignored the cold fusion reactions in the synthesis of SHE>113. This may be due to the improper choice of projectiles. The present study focusses on cold fusion reactions leading to the formation of SHE from Z = 112 to 126. Suitable projectiles for the fusion reaction using $^{208}$Pb and $^{209}$Bi targets were identified. The fusion and evaporation residue cross-sections are evaluated usingadvance statistical model. The produced cross-sections were compared with the available experiments. Suitable projectiles for synthesising the superheavy elementswith Z = 104–126 using lead and bismuth targets are predicted.The predicted production cross-sections vary from nanobarn (nb) to picobarn (pb). The use of spherical–spherical projectile and target yields larger cross-sections than spherical–deformed or deformed–spherical projectile andtarget combination.

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