electrochemical-etching-characterization-sharp-field-emission-points

Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. ...

Central Michigan University

The atomic mass of 136Xe has been measured by comparing cyclotron frequencies of single ions in a Penning trap. The result, with 1 standard deviation uncertainty, is M(136Xe)=135.907 214 484 (11) u. Combined with previous results for the mass of 136Ba [Audi, Wapstra, and Thibault, Nucl. Phys. A 729, 337 (2003)10.1016/j.nuclphysa.2003.11.003], this gives a Q value (M[136Xe]-M[136Ba])c(2)=2457.83(37) keV, sufficiently precise for ongoing searches for the neutrinoless double-beta decay of 136Xe.

Mass and double-beta-decay Q value of 136Xe.

By trapping pairs of ions in a Penning trap, alternating each ion between large and small cyclotron orbits, we have measured the cyclotron frequency ratios 12C2H4+/28Si+, 13C2H2+/28Si+, 28SiH3+/31P+, and 16O2+/31PH+, all to <30 ppt precision. The 16O2+/31PH+ data exhibit a bimodal distribution due to the polarizability of the Lambda-doubling components of the PH+ ground state, from which we obtain the electric dipole moment of 31PH+, 0.331(8) ea0. Combined with other atomic mass measurements we also obtain improved values for m(28Si), 27.976 926 535 0(6) u, and m(31P), 30.973 761 998 9(9) u.

Dipole moment of PH+ and the atomic masses of 28Si, 31P by comparing cyclotron frequencies of two ions simultaneously trapped in a penning trap.

The atomic masses of 130Te and 130Xe have been obtained by measuring cyclotron frequency ratios of pairs of triply charged ions simultaneously trapped in a Penning trap. The results, with 1 standard deviation uncertainty, are M(130Te)=129.906 222 744(16) u and M(130Xe)=129.903 509 351(15) u. From the mass difference the double-beta-decay Q value of 130Te is determined to be Qbetabeta(130Te)=2527.518(13) keV. This is a factor of 150 more precise than the result of the AME2003 [G. Audi, Nucl. Phys. A729, 337 (2003)10.1016/j.nuclphysa.2003.11.003].

Masses of 130Te and 130Xe and double-beta-decay Q value of 130Te.

Using precision, cryogenic, Penning-trap mass spectrometry we have measured the atomic mass difference M[;{115}In]-M[;{115}Sn] to be 497.489(10) keV/c;{2}. Combined with the energy of the 3/2;{+} first excited state of ;{115}Sn [J. Blachot, Nuclear Data Sheets 104, 967 (2005)10.1016/j.nds.2005.03.003], the Q value of the ;{115}In(9/2;{+}) --> ;{115}Sn(3/2;{+}) beta decay is determined to be 155(24) eV. This confirms the inference of Cattadori [Nucl. Phys. A 748, 333 (2005)10.1016/j.nuclphysa.2004.10.025] that this small branching-ratio beta decay has the lowest-known Q value. We also report improved values of the individual atomic masses: M[;{115}In] = 114.903 878 774(16) u and M[;{115}Sn] = 114.903 344 697(17) u.

Q value of ;{115}In --> ;{115}sn(3/2;{+}): the lowest known energy beta decay.

In anticipation of results from current and future double-β decay studies, we report a measurement resulting in a (82)Se double-β decay Q value of 2997.9(3) keV, an order of magnitude more precise than the currently accepted value. We also present preliminary results of a calculation of the (82)Se neutrinoless double-β decay nuclear matrix element that corrects in part for the small size of the shell model single-particle space. The results of this work are important for designing next generation double-β decay experiments and for the theoretical interpretations of their observations.

Article	Year
Mass and double-beta-decay Q value of 136Xe. Physical review letters\| PubMed ID: 17358854	2007
Dipole moment of PH+ and the atomic masses of 28Si, 31P by comparing cyclotron frequencies of two ions simultaneously trapped in a penning trap. Physical review letters\| PubMed ID: 18352703	2008
Masses of 130Te and 130Xe and double-beta-decay Q value of 130Te. Physical review letters\| PubMed ID: 19519099	2009
Q value of ;{115}In --> ;{115}sn(3/2;{+}): the lowest known energy beta decay. Physical review letters\| PubMed ID: 19792427	2009
First direct double-β decay Q-value measurement of 82Se in support of understanding the nature of the neutrino. Physical review letters\| PubMed ID: 23383782	2013

Matthew Redshaw

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