No abstract available

No abstract available

[en] Short communication

[en] The report begins with a brief introduction, summary of activities, and lists of personnel, facilities used, publications, and presentations. Work on xanthine--tyrosine and sulfuric acid esters was completed in the project on ²⁵²Cf-plasma desorption mass spectroscopy of involatile molecules. Work is continuing in the following areas: beta--gamma directional correlations and second-class currents in nuclear beta decay (mass-20 system), beta--neutrino directional correlations in mass 8, atomic mass measurements, and ²⁵²Cf-plasma desorption mass spectroscopy of large biomolecules. (3 figures) (RWR)

No abstract available

[en] The search for second-class currents in nuclear beta decay continued with measurements of beta--gamma correlations for the mirror decays ²⁰F(β^-)²⁰Ne*(1.63) and ²⁰Na(β⁺)²⁰Ne*(1.63). The ²⁰F beta--gamma correlation was measured in beam, and the results are being compared with values obtained using the He-jet method. A careful analysis of ion velocity distributions emitted from fission fragment tracks in solids yielded new information on the nature of the process. The temperature of the microplasma formed by a fission fragment was determined to be of the order 10⁴K, and the temperature is dependent on the fission fragment's energy. A mass reflectron is being developed for high mass resolution using time-of-flight mass spectroscopy. The application of ²⁵²Cf-PDMS (plasma desorption mass spectroscopy) to new classes of involatile compounds continued. Techniques are being studied for the routine analysis of involatile species of mass greater than 2000. The report is basically descriptive in nature. 5 figures, 1 table

No abstract available

[en] An analysis of the Doppler-broadened line shapes of α-groups from the β-delayed α-decay of ²⁰Na has revealed a simple method of obtaining β⁺ - nu anisotropy coefficients which is applicable for all of the β-delayed particle emitters in the light elements. In addition, a new approach to studying the longitudinal polarization and nuclear alignment of the β-recoil has emerged from the same analysis. 8 refs., 3 figs

[en] The passage of nuclear fission fragments through thin solid films produces a fission track. Measurement of the kinetic energy and angular distribution of ion emitted from the track give evidence for the formation of a superradiant state containing a high density of molecules simultaneously excited by the intense electromagnetic field associated with the fission fragment. The radiation emitted in two narrow cones at 0⁰ and 180⁰ to the fission fragment direction develops strong hypersonic pulses by stimulated Brillouin scattering. These nonlinear processes have two effects: molecules in the fission track are electronically and vibronically excited and can undergo fast chemical reactions in the excited state, and reaction products formed on the surface have a high probability of being emitted when the hypersonic pulse reaches the surface. If the reaction products are charged, they can be characterized by mass spectrometry. Electron transfer reactions have been studied with chlorophyll-a as a model compound. Molecular aggregates of chlorophyll produce a singlet exciton state characterized by an electron exchange current within the the aggregate. This was verified directly by observing the breakup of this state into (CHl-a)⁺ and (Chl-a)-ions. Molecules that form aggregates in the solid state, mediated by hydrogen bonding where the H⁺ is weakly bound (acidic), give evidence of proton charge transfer in the singlet exciton states. Amino acids, peptides, and small oligonucleotides exhibit this reaction. Molecules forming aggregates that do not produce a charge delocalization do not form separated ion pairs in the excited state. The reactions that do occur involve charge exchange (-OH + Na⁺ → -ONa + H⁺) and cation attachment (M + Li⁺ → MLi⁺). Alpha cyclodextrin has been a good model molecule for these studies

[en] The evolution of ones research activities over the years is often a consequence of surprises and unexpected observations. Such is the case with the development of the helium jet recoil transport method in the early 1960s and what has followed since then. The use of seeded beams and supersonic jet nozzle/skimmer techniques to the He jet technology in the 1970s was directed to the development of β-recoil mass spectrometry for short-lived nuclides based on surface ionization in vacuum of monolayers of nuclear reaction products. An unexpected spin-off of these studies, was the solution of a long-standing problem in biomedical mass spectrometry - how to produce gas phase molecular ions of species that are involatile and thermally unstable. The fundamental observation was that ionizing radiation with a high LET can induce desorption and ionization of complex molecular species. This formed the basis of a mass spectrometry using 252-Cf fission fragments as an ion source. The technique is being used in biomedical research laboratories throughout the world. At the same time, experiment and theoretical programs have been initiated to deduce the mechanism of the desorption/ionization process and elements of the temporal properties of the nascent fission track