Three years ago we were putting the finishing touches on our 1% measurement of PNC optical rotation in thallium vapor [Phys. Rev. Lett. vol 74, 2658 (1995); P. A. Vetter, Thesis (1995)] which at the time provided a significant test of fundamental electroweak theory. This measurement used the standard optical rotation method that had been the basis of our parity research for two decades. [Phys. Rev. A vol 52, 1895 (1995)] Paul Vetter received his PhD on the thallium PNC experiment. For this work he shared the 1997 DAMOP dissertation prize this past Spring.
We then began testing a new technique, using electromagnetically induced transparency (EIT) to control PNC optical rotation, in order to get beyond the 1% practical limitation on accuracy due to lineshape and polarizer systematics. In the first EIT studies on a forbidden transition we used counterpropagating resonant 535-nm light to observe sharp sub-Doppler features on the 1.28 um absorption line in thallium. We have submitted a paper to Physical Review Letters describing this technique for PNC measurements. Alex Cronin will write his thesis on the thallium EIT research. The goal is to improve our measurement of optical rotation in thallium from the current 1% level to a new level of about 0.3% uncertainty, which, if analyzed with foreseeable improvements in Tl atomic theory, will make a new test of the standard model.
``Precise test of electroweak theory from a new measurement of parity nonconservation in atomic thallium" P. A. Vetter, D. M. Meekhof, P. K. Majumder, S. K. Lamoreaux, and E. N. Fortson, Phys. Rev. Lett. vol 74, 2658 (1995)
``Optical rotation technique used for a high-precision measurement of parity nonconservation in atomic lead" D. M. Meekhof, P. A. Vetter, P. K. Majumder, S. K. Lamoreaux, and E. N. Fortson, Phys. Rev. A vol 52, 1895 (1995)
``Study of electromagnetically induced transparency in thallium vapor and its use for measuring atomic parity nonconservation" A. D. Cronin, R. B. Warrington, S. K. Lamoreaux, and E. N. Fortson, Phys. Rev. Lett. 80, 3719 (1998) (PDF reprint,) (Postscript reprint, 160k)