Die experimentelle Bestimmung der Ionisationsenergien von Berkelium und Californium

Frequency tripling for resonance ionization spectroscopy (RIS) of Cd

To explore the nucleosynthesis of heavy elements in the rapid neutron-capture process, investigations on short- lived, very neutron-rich Cd isotopes are planned that require pure samples. These will be produced at the CERN-ISOLDE on-line mass separator in combination with a chemically se- lective laser ion source. The excitation scheme for resonance ionization of Cd was tested in Mainz with a copper-vapor- pumped dye laser system. Due to the high ionization potential of Cd, frequency tripling was required for the first excita- tion step.1D 228: 8n m/. Laser light with an average power of 2m Wwas obtained after frequency tripling and was suc- cessfully used for RIS test measurements on cadmi…

First Experimental Determination of the Ionization Potentials of Berkelium and Californium

Erste Messung der Ionisationsenergie von Americium und Curium

Trace analysis of plutonium in environmental samples by resonance ionization mass spectroscopy (RIMS)

Resonance ionization mass spectroscopy (RIMS) is well suited for trace analysis of long-lived radioisotopes in environmental, biological and technical samples. By multiple resonant laser excitation and ionization of the elemental atoms under investigation, an extremely high element selectivity can be achieved. In addition, isotope selectivity is obtained by subsequent mass analysis. The excellent sensitivity results from the large atomic cross-sections in the excitation–ionization process and the good detection efficiency for ions. The element selectivity of RIMS allows a simplified procedure for the chemical preparation of the samples compared to the requirements of thin sources for α-spec…

Resonance ionization mass spectroscopy for trace determination of plutonium in environmental samples

Resonance ionization mass spectroscopy (RIMS) is a sensitive and isotope selective method and well suited for trace analysis of plutonium in the environment. After the chemical isolation of plutonium from soil, air filters or urine, e.g., it is electrolytically deposited as hydroxide on a tantalum backing and covered with a thin titanium layer. By heating such a sandwich filament in the RIMS-apparatus under vacuum an atomic beam of plutonium is produced. The atoms are ionized by a three-step resonant excitation using pulsed dye lasers, and the ions are mass-selectively detected with a time-of-flight (TOF) spectrometer and a multi channel plate detector. RIMS yields a low detection limit of …

Determination of the first ionization potential of actinide elements by resonance ionization mass spectroscopy

Abstract Resonance ionization mass spectroscopy (RIMS) in the presence of an external static electric field has been used for the determination of photoionization thresholds. Extrapolation of the thresholds obtained with different electric field strengths to zero field strength directly leads to the first ionization potential (IP). The ionization potentials of the transplutonium elements americium, curium, berkelium and californium could be measured for the first time. Due to the high sensitivity of RIMS, samples of only 1012 atoms have been used. The results are: IPAm = 5.9738(2)eV, IPCm = 5.9915(2)eV, IPBk = 6.1979(2)eV and IPCf = 6.2817(2)eV. The same technique was applied to thorium, ne…

First Determination of the Ionization Potential of Americium and Curium

Determination of the first ionization potential of einsteinium by resonance ionization mass spectroscopy (RIMS)

Abstract The first ionization potential of einsteinium (IP Es ) was determined by resonance ionization mass spectroscopy (RIMS) using samples with ≤10 12 atoms of 254 Es ( T 1/2 =276 days). This method is based on the measurement of photoionization thresholds as a function of applied electric field strength, followed by extrapolation to zero field strength to yield IP Es . An atomic beam of Es was created by heating a filament on which einsteinium was electrodeposited from an aqueous solution onto a tantalum backing and covered with titanium metal. Es atoms were ionized via a three-step excitation scheme, and the ions mass-selectively detected in a time-of-flight (TOF) mass spectrometer. Th…

Recent developments in and applications of resonance ionization mass spectrometry

Resonance Ionization Mass Spectrometry (RIMS) has nowadays reached the status of a routine method for sensitive and selective ultratrace determination of long-lived radioactive isotopes in environmental, biomedical and technical samples. It provides high isobaric suppression, high to ultra-high isotopic selectivity and good overall efficiency. Experimental detection limits are as low as 106 atoms per sample and permit the fast and sensitive determination of ultratrace amounts of radiotoxic contaminations. Experimental arrangements for the detection of different radiotoxic isotopes, e.g. 236–244Pu, 89,90Sr and 99Tc in environmental samples are described, and the application of RIMS to the ul…

Determination of the first ionization potential of nine actinide elements by resonance ionization mass spectroscopy (RIMS)

The high sensitivity of RIMS enables the precise determination of the first ionization potential of actinide elements with a sample size of ≤1012 atoms. By multiple resonant laser excitation, the actinide atoms under investigation are ionized in the presence of an electric field, and the ions are mass-selectively detected in a time-of-flight spectrometer. The first ionization potential is obtained by scanning the wavelength of the laser used for the last excitation step across the ionization threshold Wth—indicated by a sudden increase of the ion count rate—at various electric field strengths. Extrapolation of Wth to electric field strength zero leads directly to the first ionization potent…