The development of high intensity lasers has permitted the study of matter in extreme conditions of density and temperature. These conditions can allow nuclear excitation of isomeric states in plasma. 201Hg is a good candidate for this study. The first excited state of 201Hg is an isomeric state of 1.565 keV excitation energy with a lifetime of 81 ns [1]. In a neutral atom, the deexcitation of this state occurs mostly by internal conversion. In specific plasma conditions of temperature and density, this nuclear state can be populated preferentially by the NEET effect (Nuclear Excitation by Electronic Transition) [2]. This is a resonant process where an atomic deexcitation may cause a nuclear excitation provided that energy and angular momentum conditions are fulfilled. In the case of 201mHg, for a charge state of 42+, the 6s1/2 to 4s1/2 atomic transition is resonant with the nuclear one [1]. To highlight the production of 201mHg in a plasma, the detection of the internal conversion electron produced during this nuclear state deexcitation is necessary. The lifetime of 81 ns is not long enough to avoid the electron background due to the plasma radiation produced during the laser interaction. However, it has been shown that for charge states higher than 30+, the deexcitation by internal conversion of 201mHg is blocked and the isomeric state lifetime increases to a few milliseconds [3]. In this condition, the ions of interest can be transported far away from the laser interaction site with an electrostatic analyzer [4]. So far, we have built an analyzer and characterized it with plasma ions produced with a Nd-Yag laser. In a first study with have considered a laser intensity of 1013 W/cm� and different targets (13Al, 29Cu, 48Cd, 73Ta). In few weeks, the spectrometer will be used on a 1014 W/cm� intensity laser to make sure that high charge states of 201Hg are produced (>30+). An X-ray spectrometer will be used to measure the charge states reached inside the plasma. The results of all these experiments will be presented. In previous study [5], the NEET rate was calculated using the average atom model. To determine if the average atom model is relevant for NEET rate calculations, we have developed a new code based on DCA calculations around the average atom model to calculate the NEET rate. A comparison between the two models will be made. Then we will present an estimation of the number of excited nuclei during a laser pulse by coupling the calculations with a hydrodynamic code.References [1]V.M�ot and al, �Half-life of the first excited state of 201Hg�, Phys. Rev. C 75, 064306 (2007) [2] G.Gosselin, Private Communication. [3] G.Gosselin, V.M�ot, P.Morel  �Modified nuclear level lifetime in hot dense plasmas� Phys. Rev. C 76, 044611  [4] E.Woryna and al, �Corpuscular diagnostics and processing methods applied in investigations of laser-produced plasma as a source of highly ionized ions� Laser Part. Beams 14, 293 (1996) [5] P.Morel and al, �Evaluation of nuclear excitation by electronic transition in 235U plasma at local thermodynamic equilibrium�, Phys. Rev. A 69, 063414 (2004)

Search for nuclear excitation by electronic transition (NEET) in 201Hg

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.