S. Schröder

Bio: S. Schröder is an academic researcher from University of Mainz. The author has contributed to research in topics: Laser cooling & Storage ring. The author has an hindex of 9, co-authored 16 publications receiving 383 citations. Previous affiliations of S. Schröder include Darmstadt University of Applied Sciences.

First laser cooling of relativistic ions in a storage ring

Abstract: The first successful laser cooling of ions at relativistic energies was observed at the Heidelberg TSR storage ring. A $^{7}\mathrm{Li}^{+}$-ion beam of 13.3 MeV was oberlapped with resonant copropagating and counterpropagating laser beams. The metastable ions were cooled from 260 K to a longitudinal temperature of below 3 K and decelerated by several keV. The longitudinal velocity distribution was determined by a fluorescence method. After laser cooling a strongly enhanced narrow peak appeared in the Schottky noise spectrum in addition to the uncooled ion distribution.

First experiments with the heidelberg test storage ring TSR

Abstract: The Heidelberg heavy ion test storage ring TSR started operation in May 1988. The lifetimes of the ion beams observed in the first experiments can be explained by interactions with the residual gas. Multiple Coulomb scattering, single Coulomb scattering, electron capture and electron stripping are the relevant processes. Electron cooling of ions as heavy as O 8+ has been observed for the first time. With increasing particle number, the longitudinal Schottky noise spectrum becomes dominated by collective waves for cooled beams, allowing a determination of velocities of sound. After correcting for these coherent distortions fo the Schottky spectrum, the longitudinal beam temperature could be extracted. The observed longitudinal equilibrium beam temperatures increase strongly with the charge of the ions. For a cooled C 6+ beam, temperatures a factor of 120 higher were measured compared to a proton beam with the same particle number. The shrinking of the beam diameter due to electron cooling was observed with detectors which measured the profile of charge-changed ions behind a bending magnet. A strong laser-induced fluorescence was detected when storing metastable 7 Li + ions in the ring. Via the Doppler effect a very accurate measurement of the ion velocity profile could be performed. First attempts to observe laser cooling failed, probably due to heating effects from intrabeam scattering and a coupling between longitudinal and transversal motion in the beam. Several experiments under preparation are outlined.

Measurement of isotope shift and hyperfine splitting of 190, 191, 193, 197 Pb isotopes by collinear laser spectroscopy

Abstract: We report here on the measurement of isotope shift and hyperfine splitting of190, 191, 193, 197Pb for the 723 nm atomic optical transition. Detailed analysis of the optical data has been done by combining them with the available muonic and electronicx-ray isotope shift data. The magnetic dipole moments and the electric quadrupole moments of the odd isotopes have been extracted from the hyperfine coupling constants of the atomic states involved in the optical transition used.

Laser cooling of stored high-velocity ions by means of the spontaneous force

Abstract: A longitudinal laser cooling of ion beams at about 5% of the velocity of light has been performed at the Heidelberg Test Storage Ring with various cooling schemes employing the spontaneous force. For a 7.29-MeV $^{9}\mathrm{Be}^{+}$ beam with an initial longitudinal temperature of 2700 K, the main characteristics of laser cooling in a storage ring are discussed. When undamped, the transverse betatron oscillations of the coasting ions limit the longitudinal temperature after laser cooling to typically 1 K. After damping the transverse motion by precooling the ions with an electron cooler, longitudinal temperatures of below 30 mK have been obtained in the subsequent laser cooling. In this case, the longitudinal ion-beam temperature can be understood as an equilibrium of the laser cooling rate with the heating rate due to intrabeam scattering. Moreover, single binary Coulomb collisions between the (still transversely hot) ions can cause such longitudinal velocity changes that ions are lost out of the critical capture range of the laser cooling force. In these two ways, intrabeam scattering imposes a substantial limit on the temperature or number of laser cooled ions in a storage ring. In our experiments, this process presently limits the ratio between the density-dependent Coulomb energy and the longitudinal thermal energy spread to a value on the order of 1, where liquid rather than gaseous behavior of the ion beam is expected to set in.

Laser-stimulated two-step recombination of highly charged ions and electrons in a storage ring.

Abstract: Two-step resonant laser-stimulated recombination of highly charged ions was performed for the first time. Nd:YAG laser pulses overlapped with an Ar[sup 18+] beam in the electron cooler of the ESR storage ring at GSI induced transitions from the continuum to the [ital n]=81 state of hydrogenlike Ar[sup 17+]. To avoid reionization in the bending magnet before reaching the detector, the [ital n]=81 population was transferred to a state well below the reionization threshold by a Ti:sapphire laser. Tuning of this laser yielded the [ital n]=81 to 36 and 37 transition-line profiles. The two-step method provides access to detailed Rydberg spectroscopy in an electron beam environment.

Recent trends in the determination of nuclear masses

Abstract: The mass of the nucleus, through its binding energy, continues to be of capital importance not only for various aspects of nuclear physics, but also for other branches of physics, notably weak-interaction studies and astrophysics. The authors first describe the modern experimental techniques dedicated to the particularly challenging task of measuring the mass of exotic nuclides and make detailed comparisons. Though tremendous progress in these and the associated production techniques has been made, allowing access to nuclides very far from stability, it is still not yet possible to produce many nuclides involved in stellar nucleosynthesis, especially the $r$ process, leaving no choice but to resort to theory. The review thus goes on to describe and critically compare the various modern mass formulas that may be used to extrapolate from the data towards the neutron drip line. Special attention is devoted to the crucial interplay between theory and experiment, showing how new measurements far from stability can considerably reduce the ambiguity in extrapolations to nuclides even further away.

New effective interactions in relativistic mean field theory with nonlinear terms and density-dependent meson-nucleon coupling

Abstract: New parameter sets for the Lagrangian density in the relativistic mean field (RMF) theory, PK1 with nonlinear sigma- and omega-meson self-coupling, PK1R with nonlinear sigma-, omega-, and rho-meson self-coupling, and PKDD with the density-dependent meson-nucleon coupling are proposed. They are able to provide an excellent description not only for the properties of nuclear matter but also for the nuclei in and far from the valley of beta stability. For the first time in the parametrization of the RMF Lagrangian density, the center-of-mass correction is treated by a microscopic way, which is essential to unify the description of nuclei from light to heavy regions with one effective interaction.

Dissociative Recombination of Molecular Ions

Abstract: 1 Introduction 2 Experimental methods 3 Theoretical methods 4 The H2+molecule 5 Diatomic hydride ions 6 Diatomic ions 7 The H3+ molecule 8 Polyatomic ions 9 Related processes 10 Applications