C. Deprun

Copper ion induced reactions on110-108-106Cd,109-107Ag and110Pd. new rhenium, osmium and iridium isotopes

By63Cu induced reactions on110Cd,108Cd,106Cd,109Ag,107Ag and110Pd targets, new isotopes were searched in the Ir, Os, Re region. Cross bombardments and excitation function measurements were used to identify newα emitting isotopes:170Ir (Eα = 6.01 ±0.01 MeV−T1/2=1.1±0.2s),169Ir (Eα=6.11±0.01 MeV−T1/2=0.4±0.1 s),168Ir (Eα =6.22±0.02 MeV,168Os (Eα=5.66±0.01 MeV−T1/2=1.9±0.1 s),167Os (Eα=5.84 ±0.01MeV −T1/2=0.65±0.15s),166Os (Eα=6.00±0.02 MeV−T1/2=0.3 ±0.1 s),165Os (Eα=6.20±0.02 MeV),169Re (Eα=5.05±0.01 MeV),168Re (5.26±0.01 MeV−T1/2=5.5 ±0.5 s). Theα-decay measurements are compared to theQα values obtained from different mass predictions.

Ca induced reactions on 141Pr and 150Sm: New gold and lead isotopes 176Au, 175Au, 185Pb

Abstract Reactions induced by a beam of 40 Ca ions on 141 Pr and 150 Sm have been studied between 180 and 290 MeV. From the characteristics of the ( 40 Ca, xn) excitation functions and from the systematics of α-decay, we deduce the existence of the following new neutron deficient nuclides: 176 Au ( E α = 6.26 ± 0.01 MeV and T α 1 2 = 1.25 ± 0.30 sec and E α = 6.29 ± 0.01 MeV), 175 Au ( E α = 6.44 ± 0.01 MeV ) and 185 Pb ( E α = 6.40 ± 0.01 MeV and 6.48 ± 0.02 MeV). New information is obtained on the α-decay of 177 Au and 187 Pb.

On the mechanism of ion formation in spontaneous desorption time-of-flight mass spectrometry

Abstract In a previous paper, the observation of spontaneous desorption (SD) of negative ions in a time-of-flight mass spectrometer has been reported. The ion emission was found to depend on a high potential difference between the target and the ion accelerating grid placed a few mm apart from it. This paper shows that the SD of ions is a secondary ion emission phenomenon in which charged particles coming from the grid surface hit the target. The incident particles are either directly extracted from the grid by the applied high electric field and/or are secondary ions of impinging charged particles generated at the sample layer surface, again by a field-induced process. Measurements of the ion multiplicity suggest multiatomic ions as incident particles. The SD effect could also be established for positive ions.

252Cf-plasma desorption mass spectrometry applied to the analysis of endotoxin Lipid A preparations

Abstract Negative-ion plasma desorption mass spectra of underivatized Lipid A preparations, isolated from the endotoxins of 16 Enterobacterial and non-Enterobacterial strains, are presented. These heterogeneous preparations gave signals—in the range m/z 1000–2200—characteristic of the bacterial family from which the Lipid A was obtained. Molecular compositions based on chemical analyses were attributed to the most abundant ions. The information provided makes plasma desorption mass spectrometry a powerful tool in relating Lipid A structures to their numerous biological activities. The method is rapid and requires only microgram quantities of Lipid A.

HIGH DESORPTION-IONIZATION YIELDS OF LARGE BIOMOLECULES INDUCED BY FAST C60 PROJECTILES

Abstract C60 molecules accelerated to MeV energies (20 MeV) have been used to induce the desorption-ionization of large biomolecules from solid samples. For a sample consisting of trypsin molecules, the secondary molecular ion emission yield is about two orders of magnitude larger than with MeV atomic ions. This is a consequence of the very high energy density deposited in solids by 20 MeV C60 projectiles that gives rise to a large amount of matter ejected after each impact. Although time-of-flight mass spectra can be recorded within a few seconds, it is more the acquisition of knowledge on mechanistic aspects, in comparison with other particle-induced desorption methods, which is the objective of obtaining these first results with energetic fullerenes.

The time-of-flight mass identification system connected to the Alice He-JET. “on-line” experimental results

Abstract A time-of-flight mass identification system connected to the Alice He-jet has been tested on-line with α and β emitters produced through known heavy-ion reactions. It is shown that masses up to 150 are well resolved. Experimental results are given and further developments are briefly described. This system is actually used for the search for exotic nuclei.

Chemical effects in the collection of mercury isotopes with the He-Jet transport method

Abstract The helium-jet system in use at Orsay is briefly described. An experiment has been performed which demonstrates the importance of the choice of the impurities added to the He gas carrier. Mercury isotopes produced in the reactions 144 Nd ( 40 Ca , x n ) 184−xHg are not collected by the helium-jet method under normal conditions. It is shown that the addition of iodine (which easily reacts with mercury) to the helium gas is a very efficient way to collect the mercury isotopes.

Plasma desorption mass spectrometry (PDMS) of folic acid and derivatives

Abstract Folic acid and derivatives, chosen either as part of the molecule or as related compounds of biological or pharmacological interest, were studied with the recent technique of plasma desorption mass spectrometry (PDMS). The influence of positive and negative ionization as well as sodium attachment were systematically investigated. Results are compared with those found in literature using other mass spectrometry technics. A direct comparison, using desorption chemical ionization (DCI) was also performed for folic acid and methotrexate. Various aspects of this work are discussed.

Développement, auprès de l'accélérateur alice, des méthodes de transport par jet d'hélium des produits de réactions nucléaires: Description et applications

Abstract The He-jet transport systems for use with the heavy-ion accelerator ALICE at Orsay are described in detail. The dependence of the gas flow rate on various parameters (pressure, length and diameter of the capillary) was investigated. Off-line measurements were carried out with a 252 Cf source. Effect on collection yield of UV radiation and additives to the helium was checked. The influence of the distance between the target and the capillary on the collection efficiency for short-lived isotopes of Yb was investigated. Some other useful are details are also discussed (collector, volume of the reaction chamber, etc.). Various applications of the He-jet method are described: particle identification, angular distribution of reaction products, mass identification of radioactive nuclei.

Analusis by 252Cf plasma desorption mass spectrometry of Bordetella pertussis endotoxin after nitrous deamination

Abstract Endotoxic lipopolysaccharides (LPSs) are the major components of Gram-negative bacterial outer membrane. Like many amphipathic molecules, they pose problems of heterogeneity, purity, solubility, and aggregation. Nevertheless, PDMS has recently have been applied to unmodified endotoxins composed of LPS having uip to five sugar units in their saccharide chain. The B. Pertussis LPSs, most of which have a dodecasaccharide domain, ahve been analysed by classical methods and the masses of the separate lipid and saccharide domains determined after rupture of the bond linking them. However, the acid treatment employed for these and most chemical analyses can also modify structures in the vicinity of the bond. In order to investigate this biologically-important region, the endotoxin was treated to nitrous deamination, which shortens the saccharide chain to five sugars, but preserves the acid-labile region of the LPS. The PDM spectrum of this derivative, which required new conditions for its desorption, confirmed the structure analysis and demonstrated the presence of at least four molecular species.