1063-7850/04/3011- $26.00 © 2004 MAIK “Nauka/Interperiodica” 0917 Technical Physics Letters, Vol. 30, No. 11, 2004, pp. 917–919. Translated from Pis’ma v Zhurnal Tekhnicheskoœ Fiziki, Vol. 30, No. 21, 2004, pp. 65–71. Original Russian Text Copyright © 2004 by Ezhov, Kozlov, Krygin, Ryzhov, Ryabov. In recent years, considerable progress has been achieved in the study of weak interactions by methods of nuclear physics [1–3] used to measure the P-odd E1 amplitude in the optical transitions of heavy atoms. A part of this amplitude that is independent of the nuclear spin and bears information about the weak charge of atomic nuclei is well studied. The measurement of this part was among the most important evidence of the existence of neutral currents. At the same time, the P-odd effects dependent on the nuclear spin remain vir- tually uninvestigated. The main contribution to the P-odd spin-dependent amplitude is due to the anapole moment of the nucleus. Therefore, the measurements of such effects provide new information about weak inter- actions in the hadronic sector. The first measurements of the spin-dependent amplitude were performed for Cs [1], where the obtained value of the anapole moment constant has proved to exceed theoretical pre- dictions. Flambaum and Murray [4] use the experimental data obtained in [1] for determining the P-odd potential constants for proton and neutron. The results signifi- cantly deviated from the corresponding values obtained from nuclear physics experiments [5]. In this context, new measurements of the P-odd potential constants for other atoms would be of considerable importance. Unfortunately, practical realization of such mea- surements using optical transitions presents an extremely complicated problem. This is related, first, to the fact that the spin-dependent P-odd effect is about 100 times as small as the spin-independent one. More- over, the hyperfine structure of the optical line is usu- ally incompletely resolved, and the spin-dependent P-odd effect is manifested only by a weak distortion of the P-odd signal profile. Therefore, in order to extract the spin-dependent part of the weak interaction ampli- tude from the measured signal, it is necessary to reli- ably determine the profile of the P-off spin-independent signal, which is by no means a simple task. In the proposed experiment, we intend to measure the spin-dependent P-odd amplitude in the transitions between hyperfine components in the ground state of 41 K isotope [6, 7]. This variant offers three principal advantages over the optical experiments performed pre- viously: (i) The absence of the contribution to the amplitude due to the spin-independent part of the P-odd interac- tion makes the P-odd signal determined completely by the nuclear-spin-dependent part of the weak interaction Hamiltonian. (ii) A record small value is achieved for the rate of spin relaxation of the polarization of atoms into cells for the transitions between hyperfine sublevels of the ground state. This provides conditions for reaching an extremely high statistical sensitivity with respect to the P-odd signal. (iii) The transition frequency for the 41 K isotope in a strong constant magnetic field can be reduced to 60 MHz. This allows a cell with a characteristic size on the order of 3 cm to be arranged in the electric field antinode (and, accordingly, in the magnetic field node) so as to suppress the P-even amplitude of the magnetic dipole transition by several orders of magnitude. More- over, it is possible to provide for an additional suppres- sion of the background M1 transition in a strong mag- netic field. Indeed, when the magnetic field strength varies in the range 400–4000 G, the magnetic transition amplitude changes by an order of magnitude, while the frequency and the P-odd amplitude remain virtually unchanged. This circumstance allows us to control the On the Possibility of Measuring the Anapole Moment of Potassium Atom V. F. Ezhov, M. G. Kozlov, G. B. Krygin, V. A. Ryzhov, and V. L. Ryabov St. Petersburg Institute of Nuclear Physics, Russian Academy of Sciences, Gatchina, Leningrad oblast, Russia e-mail: http://www.pnpi.spb.ru/ Received April 22, 2004 Abstract—We suggest measuring the nuclear-spin-dependent P-odd amplitude in the transitions between hyperfine structure sublevels in the ground state of potassium isotopes. Since the main contribution to this amplitude is due to the anapole moment of the nucleus, such measurements of the P-odd spin-dependent effects may provide new information about weak interactions. It is established that the measurement of such effects with a statistical error within 1% can be performed for approximately 1 h. © 2004 MAIK “Nauka/Interperiodica”.