Engineering topics

Gottwald, T.

Publications and source records attributed to Gottwald, T..

5 records

DOE OSTI2017

Resonant ionization spectroscopy of autoionizing Rydberg states in cobalt and redetermination of its ionization potential

We obtained multi-step resonance ionization spectroscopy of cobalt using a hot-cavity laser ion source and three Ti:Sapphire lasers. Furthermore, the photoionization spectra revealed members of five new autoionizing Rydberg series that originate from three different lower levels of 3d 7 4s5s h 4 F 9/2 , 3d 7 4s4d f 4 G 11/2 , and 3d 7 4s4d f 4 H 13/2 and converge to the first four excited states of singly ionized Co. Our 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 obtained an overall ionization efficiency of about 18% for Co.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2015

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 3d 5 4s5s f 6 S 5/2 level at 49 415.35 cm -1 , while Rydberg transitions were reached from the 3d 5 4s4d e 6 D 9/2,7/2,5/2 levels at around 47 210 cm -1 . Analyses of the strong Rydberg transitions associated with the 3d 5 4s4d e 6 D 7/2 lower level indicate that they belong to the dipole-allowed 4d→nf 6 F° 9/2,7/2,5/2 series converging to the 3d 5 4s 7 S 3 ground state of Mn II. From this series, an ionization potential of 59 959.56 ± 0.01 cm -1 is obtained for Mn. At high ion source temperatures the semi-forbidden 4d→nf 8 F° 9/2,7/2,5/2 series was also observed. The overall ionization efficiency for Mn has been measured to be about 0.9% when using the strong AI transition in the third excitation step and 0.3% when employing an intense Rydberg transition. Ultimately, our experimental data indicate that the ionization efficiency was limited by the interaction of Mn atoms with ion source materials at high temperatures.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2013

Resonant three-Photon Ionization Spectroscopy of Atomic Fe

Laser spectroscopic investigations on high-lying states around the ionization potential in the atomic spectrum of Fe have been carried out for 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 63737.686 ± 0.068 cm-1 for the ionization potential of iron.

Liu, Yuan↗

DOE OSTI2012

Beam Purification by Photodetachment

Ion beam purity is of crucial importance to many basic and applied studies. Selective photodetachment has been proposed to suppress unwanted species in negative ion beams while preserving the intensity of the species of interest. A highly efficient technique based on photodetachment in a gas-filled radio frequency quadrupole ion cooler has been demonstrated. In off-line experiments with stable ions, up to 104 times suppression of the isobar contaminants in a number of interesting radioactive negative ion beams has been demonstrated. For selected species, this technique promises experimental possibilities in studies on exotic nuclei, accelerator mass spectrometry, and fundamental properties of negative atomic and molecular ions.

Liu, Yuan↗

DOE OSTI2012

Laser Ion Source Development at HRIBF

This report describes the efforts made to develop a resonant-ionization laser ion source based on tunable Ti:Sapphire lasers for nuclear physics and astrophysics research at HRIBF. Three Ti:Sapphire lasers have been upgraded with individual pump lasers to eliminate laser power losses due to synchronization delays. Ionization schemes for 14 elements have been obtained. Off-line studies show that the overall efficiency of the laser ion source can be as high as 40%. TaC surface coatings have been investigated for minimizing surface and bulk trapping of the atoms of interest.

Liu, Yuan↗