Session J10 - Electro Weak Interactions.
CONTRIBUTED session, Sunday morning, April 20
Room 5, Renaissance
Experimental measurements of ultraviolet and visible emission from two samples containing ^233U suggest the deexcitation of a purported 3.5 eV isomeric level in ^229Th(R.G. Helmer and C.W. Reich, Phys. Rev. C 49), 1845(1994).. This level is populated approximately 2% of the time in \alpha-decay of ^233U. The unique phenomenon of ultraviolet gamma-ray emission was observed. Results are consistent with theoretical arguments(V.F. Strizhov and E.V. Thalya, Zh. Eksp. Teor. Fiz. 99), 697(1991), [Sov. Phys. JETP 72, 238(1991)]. suggesting that the nucleus can deexcite via an inelastic electronic bridge mechanism, and the branching ratios for the electronic bridge and direct gamma-ray emission differ for two samples studied. Other origins of the optical photons observed such as molecular fluorescence or scintilation have been ruled out as the samples could not be excited with either ultraviolet or intense gamma radiation, which were capable of exciting fluorescence of uranyl ions in uranyl nitrate and uranium glass, as well as zinc sulphide. These observations indicate the exotic phenomenon of nuclear emission in the optical band, and open new areas of physics related to nuclear/atomic interaction. Based on the results of these measurements we report a new value for the energy of the low-lying level in ^229Th of 3.67\pm0.03~eV.