"NUCLEAR TRANSITIONS AND NEW STANDARDS OF LENGTH AND TIME"
Alexander Pasternak, Ioffe PTI of Russian AS
(id #100)
Seminar: YesPoster: No
Invited talk: No
The definition of the meter based on fundamental constant – speed of light c and the fundamental ratio c = λν. So, now wavelength of any light source, if its frequency is measured, becomes a standard of length with adequate accuracy. This accuracy is defined by the frequency stability of metrological lasers. The best stability and reproducibility was achieved due to sub Doppler spectroscopy of molecular or atom transitions; typical value for relative reproducibility now is 10-11 ÷ 10-13. It looks that this direction is close to limit.But a lot of expected achievements of 21 century in the fields of nanotechnologies, computers, GPS, astrophysics, metrology etc. are connected with an increasing of the accuracy of time and length measurements. The cardinal way of the improvement the laser frequency reproducibility is to find nuclear transitions of extremely low energies coincident with any laser line or its harmonic, because nuclear transitions almost absolute independence from temperature.
Nowadays significant efforts are devoted to the investigation of 3/2+ - 5/2+ transition of 229Th (last reported value is 7.6 ± 0.5 eV [1]). In principle the transition could be tested by comb-generator, but this way looks very difficult due to extremely narrow line widths (~10-4 Hz). In spite of this there are some projects for resolving this problem, in particular, using intensity synchrotron beams [2]. But in any case 229Th is very hard-to-reach and inconvenient material; so alternative nuclear transitions in optical range have to be found and studied. One possibility is the nuclear transition of 73 eV in 235U. Proposal of J.L. Hall [3] regarding the pumping of 181Tl (6 keV) and 57Fe (14 keV) by comb-generator and lasers with non-linear crystals for generating high harmonics shows the availability of these efforts. Important to emphasize that transitions-candidate can populate not only ground levels but also isomeric excited nuclear states, especially in heavy odd-odd nuclei. We propose to make efforts in further investigation of 229Th and for searching of new nuclear transitions.
1. B.R.Beck et. al. // Phys. Rev. Lett. 2007. V.98. P. 142501.
2. Wade G. Rellerge et. al. // Phys. Rev. Lett. 2010. V. 104. P. 200802
3. J.L.Hall, Nobel Prize lecture on physics // The Nobel Foundation 2005.
Nowadays significant efforts are devoted to the investigation of 3/2+ - 5/2+ transition of 229Th (last reported value is 7.6 ± 0.5 eV [1]). In principle the transition could be tested by comb-generator, but this way looks very difficult due to extremely narrow line widths (~10-4 Hz). In spite of this there are some projects for resolving this problem, in particular, using intensity synchrotron beams [2]. But in any case 229Th is very hard-to-reach and inconvenient material; so alternative nuclear transitions in optical range have to be found and studied. One possibility is the nuclear transition of 73 eV in 235U. Proposal of J.L. Hall [3] regarding the pumping of 181Tl (6 keV) and 57Fe (14 keV) by comb-generator and lasers with non-linear crystals for generating high harmonics shows the availability of these efforts. Important to emphasize that transitions-candidate can populate not only ground levels but also isomeric excited nuclear states, especially in heavy odd-odd nuclei. We propose to make efforts in further investigation of 229Th and for searching of new nuclear transitions.
1. B.R.Beck et. al. // Phys. Rev. Lett. 2007. V.98. P. 142501.
2. Wade G. Rellerge et. al. // Phys. Rev. Lett. 2010. V. 104. P. 200802
3. J.L.Hall, Nobel Prize lecture on physics // The Nobel Foundation 2005.
