Low-field mobilities of rare-earth metals Laatiaoui, M.; Backe, H.; Habs, D. ...
The European physical journal. D, Atomic, molecular, and optical physics,
09/2012, Letnik:
66, Številka:
9
Journal Article
Recenzirano
In this paper, a dedicated ion mobility spectrometer for heavy element research will be presented. Like most advanced mobility spectrometers, the presented apparatus is equipped with a mass ...spectrometer for isotope-selective detection. In addition, the sample atoms are ionized by exploiting the element-selective laser resonance ionization techniques. First systematic studies at various lanthanide elements have shown that their low-field mobilities in argon are quite similar. The only exception is the element gadolinium, which exhibited an 8% lower reduced mobility of 1.692(24) cm
2
/V s. This anomaly is assumed to be a direct consequence of occupying the
d
- instead of an
f
-orbital in singly charged gadolinium, which in turn has a significant impact on the gadolinium-argon interaction potential.
.
Electron capture decay of
258
Db was measured directly via delayed coincidences between
K
X-rays and/or conversion electrons (from the electron capture decay), and spontaneous fission or
α
decay of ...the daughter nuclide
258
Rf. Delayed
K
X-rays were also measured in prompt coincidence with conversion electrons, showing that electron capture decay also populates excited levels in the daughter nucleus. Our data indicate electron capture decay from two states in
258
Db, thus supporting the existence of two long-lived states in
258
Db with some seconds half-life already known from
α
-decay studies. The analysis of correlations between photons, conversion electrons and fission events resulted in a strong evidence for population of two isomeric states in
258
Rf by the electron capture decay of
258
Db, with half-lives of
T
1
/
2
=
(
15
±
10
)
μs and
T
1
/
2
=
(
2
.
4
-
0
.
8
+
2
.
4
)
ms. A previously reported
α
branch of
258
Rf was confirmed. However, we obtained a significantly lower branching ratio
b
α
=
(
0
.
049
±
0
.
016
)
. The technique is discussed as a possible new method for
Z
-identification of odd-odd superheavy nuclei.
With the Penning-trap mass spectrometer SHIPTRAP at GSI, Darmstadt, it is possible to investigate exotic nuclei in the region of the heaviest elements. Few years ago, challenging experiments led to ...the direct measurements of the masses of neutron-deficient isotopes with Z = 102; 103 around N = 152. Thanks to recent advances in cooling and ion-manipulation techniques, a major technical upgrade of the setup has been recently accomplished to boost its efficiency. At present, the gap to reach more rare and shorter-lived species at the limits of the nuclear landscape has been narrowed.
Optical spectroscopy of a primordial isotope has traditionally formed the basis for understanding the atomic structure of an element. Such studies have been conducted for most elements and ...theoretical modelling can be performed to high precision, taking into account relativistic effects that scale approximately as the square of the atomic number. However, for the transfermium elements (those with atomic numbers greater than 100), the atomic structure is experimentally unknown. These radioactive elements are produced in nuclear fusion reactions at rates of only a few atoms per second at most and must be studied immediately following their production, which has so far precluded their optical spectroscopy. Here we report laser resonance ionization spectroscopy of nobelium (No; atomic number 102) in single-atom-at-a-time quantities, in which we identify the ground-state transition
S
P
. By combining this result with data from an observed Rydberg series, we obtain an upper limit for the ionization potential of nobelium. These accurate results from direct laser excitations of outer-shell electrons cannot be achieved using state-of-the-art relativistic many-body calculations that include quantum electrodynamic effects, owing to large uncertainties in the modelled transition energies of the complex systems under consideration. Our work opens the door to high-precision measurements of various atomic and nuclear properties of elements heavier than nobelium, and motivates future theoretical work.
The superheavy element with atomic number Z=117 was produced as an evaporation residue in the (48)Ca+(249)Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The ...radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope (294)117 and its decay products. A hitherto unknown α-decay branch in (270)Db (Z = 105) was observed, which populated the new isotope (266)Lr (Z = 103). The identification of the long-lived (T(1/2) = 1.0(-0.4)(+1.9) h) α-emitter (270)Db marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an "island of stability."
Laser resonance ionization spectroscopy was performed on the rare einsteinium isotopes Es253-255 at the RISIKO mass separator in Mainz. With low sample sizes ranging down to femtograms, the prominent ...352 nm-ground-state transition was measured in all three einsteinium isotopes, and four additional ground-state transitions were measured in Es254. Hyperfine-structure analysis resulted in assigned spin values of I(Es254)=7 and I(Es255)=7/2. From the extracted coupling constants, nuclear magnetic dipole moments of μI(Es254)=3.42(7)μN and μI(Es255)=4.14(10)μN as well as spectroscopic electric quadrupole moments of Qs(Es254)=9.6(1.2)eb and Qs(Es255)=5.1(1.7)eb were derived. Our value for Es254 deviates from the value of |μI(Es254)|=4.35(41)μN extracted from the angular anisotropy of α-radiation emitted by Es254.
Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic ...multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability. The technique is characterized in a measurement on actinium isotopes around the N=126 neutron shell closure. A significant improvement in the spectral resolution by more than one order of magnitude is achieved in these experiments without loss in efficiency.
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