[en] A series of thirteen regiospecifically chlorine-37 labeled polychlorodibenzo-p-dioxins were synthesized via the Sandmeyer reaction. Nitrochlorodibenzodioxins which were obtained by a base promoted condensation of catechols and dinitropolyhalobenzenes were reduced and converted to the diazonium salts. Chlorine-37 was introduced using cuprous chloride-37. The isotopic enrichment was in the range 75-96%. (Author)

No abstract available

No abstract available

[en] With this method the element whose isotopes are to be separated is selectively excited by laser radiation and the excited isotope is brought in contact with a reaction partner (scavenger). In order to enrich ³⁷Cl vaporous iodine monochloride in acetylene is exposed to the radiation of a rhodamine-GG dye laser resulting in the formation of cis-1.2-iodine-chlorine-acetylene. For enrichment of a chlorine isotope resp. of ³⁴S or ³⁶S there is used a mixture of Cl₂ and SO₂, irradiated by 4200 A resp. 3500-3800 A, and the additive reaction Cl₂ + SO₂ → SO₂Cl₂. With the same mixture one of the oxygen isotopes ¹⁷O and ¹⁸O can be excited. (RW)

[en] Highlights: • The vibronic and cation spectra of 4-chlorostyrene are recorded. • The electronic excitation and ionization energies are precisely determined. • The spectra show a frequency shift for the isotopologues of 4-chlorostyrene. The first electronic excitation and adiabatic ionization energies of ³⁵Cl and ³⁷Cl 4-chlorostyrene were similar, with values of 33,977 ± 2 and 67,972 ± 5 cm⁻¹, respectively. The general features in the obtained vibronic and cation spectra of the two isotopologues were similar. A frequency shift of 1–5 cm⁻¹ was observed on many active vibrations of the ³⁵Cl and ³⁷Cl isotopologues of 4-chlorostyrene in the S₁ and D₀ states. This frequency difference at each mode may reflect the degree of Cl atom involvement in the overall vibration.

[en] [³⁷Cl₂]Chloramphenicol was synthesized from D-threo-2-amino-1-(4-nitrophenyl)-1,3-propanediol and ethyl[³⁷Cl ₂]dichloroacetate. Ethyl[³⁷Cl₂]dichloroacetate was prepared by chlorination with ³⁷Cl₂ of ethyldiazoacetate. ³⁷Cl₂ was obtained by reaction of a solution of Na³⁷Cl in 30% hydrogen peroxide with fuming sulfuric acid. The overall yield (from Na³⁷Cl) was 36%. (author)

[en] In 1986-87, when the speaker first became involved in neutrino studies at BNL, the GALLEX collaboration was forming and the Gran Sasso Underground Laboratory was being built in Italy. The key scientific questions at that time were: First, is the solar neutrino deficit claimed by BNL's Ray Davis et al. real? And, second, if yes, then what is the explanation? At that time, only two neutrino experiments were operating: Ray's chlorine-37 radiochemical neutrino detector in the U.S., and the real-time detector, Kamiokande, in Japan. Since then, several new experiments -- GALLEX, SAGE, Super-Kamiokande, SNO (Sudbury Neutrino Observatory), and KamLAND -- have obtained significant results that have greatly expanded our understanding of neutrino physics. SNO plus Super-Kamiokande solved the long-standing solar neutrino problem -- and Ray Davis won the Nobel Prize. So, people in the neutrino field say that we have left the era of discovery and have recently entered an era of precision 'New Physics,' during which we will learn about the detailed properties of neutrinos, such as their masses and their mixing angles. In this talk, the speaker will review highlights of the last 20 years and discuss a few ideas for new precision neutrino experiments, some of which will involve collaborative efforts of his group in the Chemistry Department and colleagues in the Physics Department.

[en] The saline spring 'Fonte da Pipa' (or 'Fonte da Bica', as there is some dispute on the name) is the only remaining actively exploited terrestrial salina in Portugal. The spring contains some 137 gram per liter dissolved solids of which 97% is NaCl. The salt is extracted from this brine in a two-stage process and commercialized by the 'Cooperativa Agricola dos Produtores de Sal de Rio Maior'. Despite its importance to the local economy, both as a natural resource and a tourist attraction its geochemistry has never been studied beyond one preliminary water analysis in 1936. In this study we have used stable Cl isotopes to develop a model for the origin of the saline spring. As this spring contains nearly pure NaCl it also is a perfect location to study progressive Cl isotope fractionation during evaporation processes

[en] The Christiansen-filter technique was used to measure the coherent scattering lengths b for the bound atoms of the chlorine isotopes ³⁵Cl and ³⁷Cl. The results are b(Cl-35) = 11.70 +- 0.09 fm/atom and b(Cl-37) = 3.08 +- 0.06 fm/atom. Furthermore, the total cross section of natural chlorine for neutron energies 1.2 eV and 5.2 eV was determined by means of transmission measurements with rotating resonance detectors. From these data the spin state scattering lengths a+(J = 2) and a-(J = 1) were obtained for the free nuclei of the isotopes. The derived values of the spin- and isotopically incoherent scattering cross section at 'zero energy' are well consistent with previously published resonance data. The present results combined with the resonance parameters make possible a complete description of the interaction of slow neutrons with the chlorine nuclei. (orig.)

[en] The ³⁷Cl(³He, αγ)³⁶Cl reaction was studied at 18 MeV, using an enriched CaCl₂ target. The γ rays coincident with the α particles emitted at forward angle were detected by two Ge(Li) detectors located at theta=90degree and 125degree. Forty-two levels were observed in ³⁶Cl, essentially those seen in the (p,d) reaction. The γ-decay schemes of the two lowest lying T=2 levels of ³⁶Cl (analogs of the first two levels of ³⁶S, J/sup pi/=0⁺ and 2⁺, respectively) have been determined. The lowest T=2 level at E/subx/=4299.5+-1.1 keV, feeds three levels: E/subx/=1165 keV (J/sup pi/=1⁺, 65+-8%), E/subx/=1601 keV (J/sup pi/=1⁺, 28+-5%), and E/subx/=2677 keV (J/sup pi/=1⁺, 7+-3%). The second one at E/subx/=7564+-4 keV feeds the levels at E/subx/=1601 keV (42+-6%), E/subx/=1960 keV (J/sup pi/=2⁺, 40+-6%), and E/subx/=2491 keV (J/sup pi/=2⁺, 18+-4%). These decay schemes are compared with shell model predictions. Some other levels of ³⁶Cl are also discussed