The development of high-intensity lasers is opening up new opportunities for nuclear-physics studies. Lasers are promising tools to study nuclear properties in extreme plasma conditions, which cannot be reached with conventional particle accelerators. In a plasma, the interaction between a nucleus and its electronic cloud can be influenced by its environment and unusual excitation processes such as nuclear excitation by electronic capture (NEEC) and nuclear excitation by electronic transition (NEET) should be observed. Indeed, NEEC (unobserved) and NEET (observed in 197Au [1], 189Os [2,3] and 193Ir [4] in accelerator based experiments) are exotic processes relevant to astrophysics, which can be dominant in particular plasma conditions of temperature and density [5], and therefore it is highly desirable to study them. These two processes involve a coupling between the nucleus and the electronic cloud. In the case of the NEET, a bound-bound atomic transition leads to a nuclear excitation if the two transitions are resonant and have the same multipolarity. The NEEC process is equivalent to the NEET process with the difference that the atomic transition is bound-free. We have undertaken a joint experimental and theoretical program to investigate the 84mRb excitation rate in laser produced plasma. The long-lived isomeric state of the 84Rb (energy of 463.6 keV, T1/2=20.26min) can be excited towards a higher lying short-lived state. According to the literature, the nuclear transition energy involved in this excitation is 3.05 (20) keV. It is possible to find atomic transitions, which match this nuclear transition for charge states between 27+ and 32+ allowing the NEET process to take place [6].Searching for the NEET process in plasma requires an accelerator to produce the 84Rb isomeric state and a high-energy- high-intensity laser to create the plasma with the required charge states. This kind of facility exists at GSI (Darmstadt, Germany) where the PHELIX high-energy laser is combined with the UNILAC ion accelerator.To prepare the NEET experiment, nuclear and atomic physics experiments were conducted. We have made experiments at ELSA (CEA/DAM, Bruy�res-le-Ch�tel) and at TANDEM/ALTO (Orsay) accelerators to measure the nuclear transition energy with high accuracy. Indeed, the accuracy of this transition energy in the tables was insufficient (200 eV) in comparison with the accuracy of the atomic data (few eV) [7]. We have also measured the X-ray spectra emitted by a Rb plasma at PHELIX. These spectra will be compared with theoretical ones to determine plasma conditions (charge states, temperature�) reached during the experiment. The results of these experiments will be presented. References [1] S. Kishimoto et al., �Observation of Nuclear Excitation by Electron Transition in 197Au with Synchrotron X Rays and an Avalanche Photodiode�,Phys. Rev. Lett. 85 ,1831 (2000) [2] I. Ahmad et al., �Nuclear excitation by electronic transition in 189Os�,  Phys. Rev. C 61 , 051304 (2000) [3] K. Aoki et al., �Probability of nuclear excitation by electron transition in Os atoms�,  Phys. Rev. C 64 , 044609 (2001) [4] S. Kishimoto et al.,�Evidence for nuclear excitation by electron transition on 193Ir and its probability�, Nucl. Phys. A 748 , 3 (2005) [5] F.Gobet et al., �Nuclear physics studies using high energy lasers�, Nucl. Instrum. Methods Phys. Res. A 653 , 80 (2011)[6] G. Gosselin. Private communication.[7]F.G. Kondev, Nuclear Data Sheets110 , 2815 (2009)

NEET in plasma: The case of <sup>84 </sup>Rb

248th National Meeting (2014)

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NEET in plasma: The case of 84 Rb

NEET in plasma: The case of ⁸⁴Rb