0000000000309028
AUTHOR
T. Gottwald
Excited atomic energy levels in protactinium by resonance ionization spectroscopy
We present high-resolution data of the single-excitation spectrum of protactinium, reaching slightly beyond the first-ionization threshold. Within this work, more than 1500 energy levels are recorded in different excitation energy ranges below $50\phantom{\rule{0.16em}{0ex}}000\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. Our experimental results show that the tabulated data in the literature severely underestimate the density of states particularly regarding the highly excited spectral range.
Resonant Ionization Laser Ion Source for Radioactive Ion Beams
A resonant ionization laser ion source based on all‐solid‐state, tunable Ti:Sapphire lasers is being developed for the production of pure radioactive ion beams. It consists of a hot‐cavity ion source and three pulsed Ti:Sapphire lasers operating at a 10 kHz pulse repetition rate. Spectroscopic studies are being conducted to develop ionization schemes that lead to ionizing an excited atom through an auto‐ionization or a Rydberg state for numerous elements of interest. Three‐photon resonant ionization of 12 elements has been recently demonstrated. The overall efficiency of the laser ion source measured for some of these elements ranges from 1 to 40%. The results indicate that Ti:Sapphire lase…
Determination of a three-step excitation and ionization scheme for resonance ionization and ultratrace analysis of Np-237
Abstract The long-lived radio isotope 237 Np is generated within the nuclear fuel cycle and represents a major hazard in the final disposal of nuclear waste. Related geochemical research requires sensitive methods for the detection of ultratrace amounts of neptunium in environmental samples. Resonance ionization mass spectrometry (RIMS) has proven to be one of the most sensitive methods for the detection of plutonium. A precondition for the application of RIMS to ultratrace analysis of neptunium is the knowledge of an efficient and selective scheme for optical excitation and ionization. Therefore, a multitude of medium to high-lying atomic levels in neptunium was located by applying in-sour…
Depletion of the excited state population in negative ions using laser photodetachment in a gas-filled RF quadrupole ion guide
International audience; The depopulation of excited states in beams of negatively charged carbon and silicon ions was demonstrated using collisional detachment and laser photodetachment in a radio frequency quadrupole ion guide filled with helium. The high lying, loosely bound 2 D excited state in C − was completely depleted through collisional detachment alone, which was quantitatively determined within 6%. For Si − the combined signal from the population in the 2 P and 2 D excited states was only partly depleted through collisions in the cooler. The loosely bound 2 P state was likely to be completely depopulated and the more tightly bound 2 D state was partly depopulated through collision…
Three-photon resonance ionization of atomic Mn in a hot-cavity laser ion source using Ti:sapphire lasers
Three-photon resonance ionization of atomic manganese (Mn) in a hot-cavity ion source using Ti:sapphire lasers has been demonstrated. Three-step ionization schemes employing different intermediate levels and Rydberg or autoionizing (AI) states in the final ionization step are established. Strong AI resonances were observed via the 3d54s5s f 6S5/2 level at 49 415.35 cm−1, while Rydberg transitions were reached from the 3d54s4d e 6D9/2,7/2,5/2 levels at around 47 210 cm−1. Analyses of the strong Rydberg transitions associated with the 3d54s4d e 6D7/2 lower level indicate that they belong to the dipole-allowed 4d → nf 6F°9/2,7/2,5/2 series converging to the 3d54s 7S3 ground state of Mn II. Fro…
Time profile of ion pulses produced in a hot-cavity laser ion source.
The time spreads of Mn ions produced by three-photon resonant ionization in a hot-cavity laser ion source are measured. A one-dimensional ion-transport model is developed to simulate the observed ion time structures. Assuming ions are generated with a Maxwellian velocity distribution and are guided by an axial electric field, the predictions of the model agree reasonably well with the experimental data and suggest that the ions are radially confined in the ion source and a substantial fraction of the ions in the transport tube are extracted.
Resonant ionization spectroscopy of autoionizing Rydberg states in cobalt and redetermination of its ionization potential
Multi-step resonance ionization spectroscopy of cobalt has been performed using a hot-cavity laser ion source and three Ti:Sapphire lasers. The photoionization spectra revealed members of five new autoionizing Rydberg series that originate from three different lower levels of 3d74s5s h4F9/2, 3d74s4d f4G11/2, and 3d74s4d f4H13/2 and converge to the first four excited states of singly ionized Co. The analyses of the Rydberg series yield 63564.689 �� 0.036 cm-1 as the first ionization potential of Co, which is an order of magnitude more accurate than the previous estimation. Using a three-step resonance ionization scheme that employs an autoinizing Rydberg state in the last transition, we obta…
The laser ion source and trap (LIST) – A highly selective ion source
A combined structure consisting of a laser ion source and a linear Paul trap (LIST) has been designed to produce radioactive ion beams of high purity and optimal temporal and spacial brilliance at on-line isotope separator (ISOL) facilities. The functionality of the LIST was experimentally demonstrated in off-line tests using the RISIKO off-line mass separator together with an all solid state Ti:sapphire laser system at the University of Mainz. Two different ion trap designs were tested extracting the performance of these devices regarding ionization efficiency and selectivity as well as time structure and transverse emittance of the produced ion beam. The results of these measurements are …
Determination of the first ionization potential of technetium
Using resonance ionization spectroscopy the first-ionization potential of actinium has been determined by analyzing different Rydberg series in two-color resonant laser excitation. Three individual Rydberg series were investigated, converging toward the ionic ground state and toward the first- and second-excited state of the actinium ion, respectively. A combined analysis of the convergence limits leads to a consistent value for the first-ionization potential of Ac of $43\phantom{\rule{0.16em}{0ex}}394.45\phantom{\rule{0.16em}{0ex}}(19)\phantom{\rule{0.28em}{0ex}}{\text{cm}}^{\ensuremath{-}1}$, equivalent to $5.380\phantom{\rule{0.16em}{0ex}}226\phantom{\rule{0.16em}{0ex}}(24)$ eV.
Ion production from solid state laser ion sources.
Laser ion sources based on resonant excitation and ionization of atoms are well-established tools for selective and efficient production of radioactive ion beams. Recent developments are focused on the use of the state-of-the-art all solid-state laser systems. To date, 35 elements of the periodic table are available from laser ion sources based on tunable Ti:sapphire lasers. Recent progress in this field regarding the establishment of suitable optical excitation schemes for Ti:sapphire lasers are reported.
Resonant three-photon ionization spectroscopy of atomic Fe
Laser spectroscopic investigations on high-lying states around the ionization potential (IP) in the atomic spectrum of Fe have been carried out for the development of a practical three-step resonance ionization scheme accessible by Ti: sapphire lasers. A hot cavity laser ion source, typically used at on-line radioactive ion beam production facilities, was employed in this work. Ionization schemes employing high-lying Rydberg and autoionizing states populated by three-photon excitations were established. Five new Rydberg and autoionizing Rydberg series converging to the ground and to the first four excited states of Fe II are reported. Analyses of the Rydberg series yield the value 63 737.68…
Optical spectroscopy and performance tests with a solid state laser ion source at HRIBF
An ISOLDE-type hot-cavity laser ion source based on high-repetition-rate Ti:Sapphire lasers has been set up at the Holifield radioactive ion beam facility. To assess the feasibility of the all-solid-state laser system for applications at advanced radioactive ion beam facilities, spectroscopy and performance tests have been conducted with this source. The results of recent studies on excitation schemes, source efficiency, beam emittance and ion time structure are presented.
The laser ion source trap for highest isobaric selectivity in online exotic isotope production
The improvement in the performance of a conventional laser ion source in the laser ion source and trap (LIST) project is presented, which envisages installation of a repeller electrode and a linear Paul trap/ion guide structure. This approach promises highest isobaric purity and optimum temporal and spatial control of the radioactive ion beam produced at an online isotope separator facility. The functionality of the LIST was explored at the offline test separators of University of Mainz (UMz) and ISOLDE/CERN, using the UMz solid state laser system. Ionization efficiency and selectivity as well as time structure and transversal emittance of the produced ion beam was determined. Next step aft…
Resonance ionization spectroscopy of thorium isotopestowards a laser spectroscopic identification of the low-lying 7.6 eV isomer of 229Th
International audience; In-source resonance ionization spectroscopy was used to identify an efficient and selective three step excitation/ionization scheme of thorium, suitable for titanium:sapphire (Ti:sa) lasers. The measurements were carried out in preparation of laser spectroscopic investigations for an identification of the low-lying 229 m Th isomer predicted at 7.6 ± 0.5 eV above the nuclear ground state. Using a sample of 232 Th, a multitude of optical transitions leading to over 20 previously unknown intermediate states of even parity as well as numerous high-lying odd parity auto-ionizing states were identified. Level energies were determined with an accuracy of 0.06 cm −1 for inte…