The search for second-class currents in nuclear beta decay continued with measurements of beta--gamma correlations for the mirror decays /sup 20/F(..beta../sup -/)/sup 20/Ne*(1.63) and /sup 20/Na(..beta../sup +/)/sup 20/Ne*(1.63). The /sup 20/F 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 10/sup 4/K, 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 /sup 252/Cf-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. (RWR)

The velocity spectrum of ${\mathrm{Cs}}^{+}$ and ${\mathrm{Br}}^{\ensuremath{-}}$ ions emitted from thin CsBr films irradiated with fission fragments show that the ions are not ejected by direct collisional interactions with the fission fragments but appear to be thermionically emitted with an average temperature of 6.6 \ifmmode\times\else\texttimes\fi{} ${10}^{4}$ K. This suggests the existence of a transient hot thermal core within the fission fragment track. Transient fission tracks in condensed phases may be convenient media for studying fast high-temperature atomic and molecular interactions.

We have shown that 252Cf-PDMS is capable of producing mass spectra of quasi-molecular ions for a wide variety of compounds, including amino acids, moderately large peptides, nucleotides, and natural products. Positive and negative ion mass spectra can be obtained, and in many cases quasi-molecular ions are observed in both. The method is nondestructive, as only a relatively few molecules are used and samples can be recovered after the measurement is made. Fragmentation patterns are obtained which can yield structure information. The present sensitivity of the method is at the nanogram level and there are possibilities for reducing this to picograms. The mass resolution is sufficient to give elemental identification up to mass 500. This may be extended to higher masses with improved time-of-flight techniques. There are indications that 252Cf-PDMS may extend the mass range of molecules that can be studied to as high as 3000 or more.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe structure of Q* nucleoside isolated from rabbit liver transfer ribonucleic acidH. Kasai, K. Nakanishi, R. D. Macfarlane, D. F. Torgerson, Z. Ohashi, J. A. McCloskey, H. J. Gross, and S. NishimuraCite this: J. Am. Chem. Soc. 1976, 98, 16, 5044–5046Publication Date (Print):August 1, 1976Publication History Published online1 May 2002Published inissue 1 August 1976https://pubs.acs.org/doi/10.1021/ja00432a071https://doi.org/10.1021/ja00432a071research-articleACS PublicationsRequest reuse permissionsArticle Views436Altmetric-Citations103LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Details of a 252Cf-plasma desorption time-of-flight mass spectrometer are described. Fission fragments from 252Cf decay are used to produce rapid heating and ionization in thin solid samples. Time-of-flight measurements are made by single ion counting using fast pulse electronics techniques. An electrostatic particle guide is used to produce an 8-m flight path for high-resolution mass measurements.

A new method has been developed to obtain mass spectra of non-volatile compounds from the solid state at room temperature. Volatilization and chemical ionization of the sample are effected using a 252Cf fission fragment source. Mass spectra are measured using a new time-of-flight mass spectrometer featuring single ion counting and fast electronics. We present positive and negative ion mass spectra for the amino acids arginine and cystine which are characterized by intense quasi-molecular ions.

A new approach to “on-line” mass identification of short-lived nuclides is described. The method is based on a time-of-flight measurement of β-recoil ions accelerated from near rest to a fixed kinetic energy. Results have been obtained for flight paths ranging from 25 to 800 cm. The shorter flight lengths give a resolution sufficient for adjacent mass identification and the longest flight path may be used to measure atomic masses of the β-recoils.

The decay scheme of $^{20}\mathrm{Na}$ has been studied in detail to obtain information on the $\ensuremath{\beta}$-decay mirror symmetry properties of the mass-20 multiplet and to determine the Fermi decay strength to the $T=1$ isobaric analog state in $^{20}\mathrm{Ne}$. The ratio $\frac{{\mathrm{ft}}^{+}}{{\mathrm{ft}}^{\ensuremath{-}}}$ was determined to be 1.026 \ifmmode\pm\else\textpm\fi{} 0.024 for the ${\ensuremath{\beta}}^{+}$ transitions to the first excited state of $^{20}\mathrm{Ne}$. The $\mathrm{ft}$ value for the transition to the $T=1, 10.278$-MeV level was measured to be 2992 \ifmmode\pm\else\textpm\fi{} 233 sec indicating that most of the Fermi strength is concentrated in this transition. A weak $\ensuremath{\gamma}$ transition from the ${2}^{+}$ isobaric analog state to the ${2}^{+}$ first excited state of $^{20}\mathrm{Ne}$ was observed and new ${\ensuremath{\beta}}^{+}$-delayed $\ensuremath{\alpha}$ groups are reported at 3.27, 5.272, and 5.701 MeV. Theoretical $\mathrm{ft}$ values derived from the shell-model wave functions are compared with experiment.

The β+-strength in the decay of 20Na to the isobaric analog state in 20Ne has been measured precisely. Contrary to previous measurements, it has been found that essentially the full Fermi strength is associated with this transition. A test of mirror symmetry has also been made for the decay to the first excited state of 20Ne. There is evidence of an asymmetry somewhat smaller than that expected from the Wilkinson systematics.

Alpha particles emitted from levels in 24Mg following the β-decay of 24Al have been measured. In addition to the α-groups previously reported in the β-decay of the 4+ ground state of 24Al, new groups were observed as a result of using special techniques to reduce the β-background and to increase particle energy resolution. Alpha-particle groups associated with the β-decay of the 1+ isomeric state of 24Al were observed for the first time. The α-particle transitions observed in this work have been correlated with known energy levels. Log ft values have been calculated or estimated from the relative intensities of the delayed α-particle groups.