We report a new measurement of parity nonconserving (PNC) optical rotation on the 6p1/2- 6p3/2 transition in atomic thallium near 1283 nm. The result expressed in terms of the quantity R=Im{E1PNC/M1} is −(15.68±0.45)×10−8, and is consistent with current calculations based on the standard model. In addition, limits have been set on the much smaller nuclear spin-dependent rotation amplitude at RS=(0.04±0.20)×10−8; this is consistent with theoretical estimates which include a nuclear anapole contribution.
Spin of the Tl nucleus is 1/2.
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