New theoretical insights on the physics of compound nuclei from laser-nucleus reactions Adriana Pálffy Max Planck Institute for Nuclear Physics, Heidelberg, Germany Laser-Driven Radiation Sources for Nuclear Applications Washington DC, Monday, December 14th 2015
Laser-nucleus reactions Adriana Pálffy Max Planck Institute for Nuclear Physics, Heidelberg, Germany VUV + nuclei X-ray + nuclei XFEL Gamma-ray + nuclei Laser-Driven Radiation Sources for Nuclear Applications Washington DC, Monday, December 14th 2015
Laser-nucleus interaction with a coherent, MeV-photons laser! Extreme Light Infrastructure Nuclear Pillar Compton backscattering of a second laser PW optical pulse Carbon foil Relativistic flying mirror G. Mourou and T. Tajima, Science 331 (2011) 41
Laser-nucleus interaction with a coherent, MeV-photons laser! Extreme Light Infrastructure Nuclear Pillar Compton backscattering of a second laser PW optical pulse ELI photons Carbon foil Relativistic flying mirror N > 103 E ~ 10 MeV T ~ 10-19 s G. Mourou and T. Tajima, Science 331 (2011) 41
Laser-atom interaction Keldysh parameter Which picture would be right for laser-nucleus interaction?
Laser-atom interaction Which picture would be right for laser-nucleus interaction? I ~ 10 MeV m ~ 2000 me ω ~ MeV
Laser-nucleus interaction PHOTOEXCITATION creates particle-hole pairs RESIDUAL INTERACTION redistributes energy over more particle-hole pairs
Laser-nucleus interaction PHOTOEXCITATION creates particle-hole pairs RESIDUAL INTERACTION redistributes energy over more particle-hole pairs
Laser-nucleus interaction QUASIADIABATIC REGIME PHOTOEXCITATION creates particle-hole pairs RESIDUAL INTERACTION redistributes energy over more particle-hole pairs after each photon absorption, the nucleus has time to equilibrate
Laser-nucleus interaction PERTURBATIVE REGIME H. A. Weidenmüller, PRL 106, 122502 (2011) QUASIADIABATIC REGIME PHOTOEXCITATION creates particle-hole pairs RESIDUAL INTERACTION redistributes energy over more particle-hole pairs after each photon absorption, the nucleus has time to equilibrate
Laser-nucleus interaction SUDDEN REGIME QUASIADIABATIC REGIME PHOTOEXCITATION creates particle-hole pairs RESIDUAL INTERACTION redistributes energy over more particle-hole pairs after each photon absorption, the nucleus has time to equilibrate
Competing channels PHOTOEXCITATION creates particle-hole pairs RESIDUAL INTERACTION redistributes energy over more particle-hole pairs
Competing channels PHOTOEXCITATION creates particle-hole pairs Bye bye and thanks for all the fish!!! NEUTRON EVAPORATION after several absorbed photons
Competing channels PARTICLE EMISSION single nucleons reach the continuum Bye bye and thanks for all the fish!!! NEUTRON EVAPORATION after several absorbed photons
Competing channels Bye bye and thanks for all the fish!!! PARTICLE EMISSION single nucleons reach the continuum Bye bye and thanks for all the fish!!! NEUTRON EVAPORATION after several absorbed photons
Competing channels Bye bye and thanks for all the fish!!! Bye bye and thanks for all the fish!!! a neutron PARTICLE EMISSION single nucleons reach the continuum NEUTRON EVAPORATION after several absorbed photons
Competing channels Bye bye and thanks for all the fish!!! Bye bye and thanks for all the fish!!! a neutron or a proton PARTICLE EMISSION single nucleons reach the continuum NEUTRON EVAPORATION after several absorbed photons
Far from yrast Dipole absorption Energy photoexcitation CN hundreds of MeV above yrast! heavy ion collisions yrast line yrast Angular momentum
Far from yrast Dipole absorption Energy photoexcitation No CN hundreds of MeV yrast! longerabove discrete levels, but level densities! heavy ion collisions yrast line yrast Angular momentum
Quasiadiabatic regime Assume complete nuclear equilibration between two photon absorptions Effective absorption rate of an equilibrated compound nucleus COMPETING WITH Induced dipole emission Induced nucleon emission Neutron evaporation Fission
Level densities needed! New theoretical formalism for high energies and high particle-hole numbers! Shell model with finite number of bound states, A spinless non-interacting fermions distributed d
Level densities needed! New theoretical formalism for high energies and high particle-hole numbers! Shell model with finite number of bound states, A spinless non-interacting fermions distributed d STEP I: CONSTANT SPACING MODEL Corrected Gaussian, 2nd, 4th, and 6th moments 51 states AP and H. A. Weidenmüller, Phys. Lett. B 718, 1105 (2013)
Level densities STEP II: REALISTIC SPACING More realistic case, level spacing linear or quadratic in energy 148 states A=100 Shift in energy Slight asymmetry Narrower width AP and H. A. Weidenmüller Nucl. Phys. A 917, 15 (2013) Density of accessible states - Fermi gas model
Level densities STEP II: REALISTIC SPACING More realistic case, level spacing linear or quadratic in energy 148 states A=100 Bethe formula Shift in energy Slight asymmetry Narrower width AP and H. A. Weidenmüller Nucl. Phys. A 917, 15 (2013) Density of accessible states - Fermi gas model
Rates Examples of rates based on newly developed nuclear level densities calculation method AP and H. A. Weidenmüller, Nucl. Phys. A 917, 15 (2013) Medium-weight, A=100 Heavy, A=200 AP and H. A. Weidenmüller, Phys. Rev. Lett. 112, 192502 (2014)
Time-dependent approach Assume complete nuclear equilibration between two photon absorptions MASTER EQUATION occupation probability Dipole absorption Induced dipole emission Neutron evaporation Fission # absorbed photons species neutron evaporation AP, O. Buss, A. Hoefer, H. A. Weidenmüller, PRC 92, 044619 (2015) fission
Results Solve in matrix form, very stiff nuclear fuel burnup and radioactivity transport codes AREVA-developed semi-analytical solver for calculation of matrix exponential only dipole absorption and emission + neutron emission + fission no proton emission (shifts decay products towards stability) AP, O. Buss, A. Hoefer, H. A. Weidenmüller, PRC 92, 044619 (2015)
Results for only dipole absorption and induced dipole emission A=100, photon energy 5 MeV Effective dipole widths (# of coherent photons in pulse) = 1 MeV = 5 MeV AP, O. Buss, A. Hoefer, H. A. Weidenmüller, PRC 92, 044619 (2015) = 8 MeV
Results Dipole absorption and induced dipole emission + neutron evaporation (T + first 3 daughters) A=100, photon energy 5 MeV, = 5 MeV no neutron decay dump AP, O. Buss, A. Hoefer, H. A. Weidenmüller, PRC 92, 044619 (2015)
Results Dipole absorption and induced dipole emission + neutron evaporation (T + first 3 daughters) + fission A=100, photon energy 5 MeV, = 5 MeV AP, O. Buss, A. Hoefer, H. A. Weidenmüller, PRC 92, 044619 (2015)
Results Dipole absorption and induced dipole emission + neutron evaporation (T + first 3 daughters) + fission A=200, photon energy 5 MeV, = 5 MeV AP, O. Buss, A. Hoefer, H. A. Weidenmüller, PRC 92, 044619 (2015)
What can we learn? Little known of fission from highly excited states! Inspection of decay products vs pulse duration/intensity/photon energy will tell us of time scales level densities decay mechanisms decay parameters
Conclusions nuclear excitation with a multi-mev zs coherent laser pulse Quasi-adiabatic regime 1 photon absorbed / nuclear relaxation time leads far from yrast and far from stability!!! excitation only possible up to the maximum of nuclear level density! proton-rich nuclei due to strong neutron evaporation, which limits the excitation fission terminates the reaction after several tens of zs, unless pulse shorter future experiments will shed light on parameters and processes involved
Assumptions equilibration between each photon absorption spinless, non-interacting particles no even-odd staggering, all nuclei are even, Fermi energy constant no particle emission would shift decay chain closer to valley of stability
Competing channels PHOTOEXCITATION creates particle-hole pairs Bye bye and thanks for all the fish!!! NEUTRON EVAPORATION after several absorbed photons
Competing channels PARTICLE EMISSION single nucleons reach the continuum Bye bye and thanks for all the fish!!! NEUTRON EVAPORATION after several absorbed photons
Competing channels Bye bye and thanks for all the fish!!! PARTICLE EMISSION single nucleons reach the continuum Bye bye and thanks for all the fish!!! NEUTRON EVAPORATION after several absorbed photons
Competing channels Bye bye and thanks for all the fish!!! Bye bye and thanks for all the fish!!! a neutron PARTICLE EMISSION single nucleons reach the continuum NEUTRON EVAPORATION after several absorbed photons
Competing channels Bye bye and thanks for all the fish!!! Bye bye and thanks for all the fish!!! a neutron or a proton PARTICLE EMISSION single nucleons reach the continuum NEUTRON EVAPORATION after several absorbed photons
Comparison AP and H. A. Weidenmüller Phys. Rev. Lett. 112, 192502 (2014)!!! At maximum of level density, photon absorption and emission are equally probable!!!