Anomalously small blackbody radiation shift in the Tl+frequency standard

Abstract

The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. In the present work, we used configuration interaction + coupled-cluster method to evaluate polarizabilities of the 6s 2 1 S0 and 6s6p 3 P0 states of Tl + ion; we find α0( 1 S0) = 19.6 a.u. and α0( 3 P0) = 21.4 a.u.. The resulting BBR shift of the 6s6p 3 P0 − 6s 2 1 S0 Tl + transition at 300 K is ∆νBBR = −0.0157( 16) Hz. This result demonstrates that near cancelation of the 1 S0 and 3 P0 state polarizabilities in divalent B + , Al + , In + ions of group IIIB [Safronova et al., PRL 107, 143006 (2011)] continues for much heavier Tl + , leading to anomalously small BBR shift for this system. This calculation demonstrates that the BBR contribution to the fractional frequency uncertainty of the Tl + frequency standard at 300 K is 1 × 10 −18 . We find that Tl + has the smallest fractional BBR shift among all present or proposed frequency standards with the exception of Al + .

Optical atomic clocks

“…Many detection schemes exist, but the most widely utilized for high performance laser stabilization is the Pound-Drever-Hall (PDH) technique. The interested reader is referred to Drever et al (1983), Day, Gustafson, andByer (1992), Hall and Zhu (1992), Zhu and Hall (1993), and Black (2001) for details on this popular scheme. Here we simply point out that PDH stabilization utilizes the laser field reflected from the optical reference cavity to detect resonance.…”

“…This effect is significant for most neutral and singly charged ion species with typical shifts on the order of hertz at room temperature . The large energy difference of the ground and excited clock states to other states connected by strong transitions results in a significantly reduced blackbody radiation shift in group 13 ions Safronova, Kozlov, and Clark, 2011;Zuhrianda, Safronova, and Kozlov, 2012). If a single atom contains two clock transitions with different sensitivity to the blackbody radiation shift (such as Yb þ ), a synthetic frequency can be established that eliminates the dominant T 4 -dependent term of the shift (Yudin et al, 2011).…”

Relativistic all-order many-body calculation of energies, wavelengths, and M1 and E2 transition rates for the 3dnSafronova1, Safronova2, Porsev3 et al. 2018Phys. Rev. ASelf Cite18190View full textAdd to dashboardCite

“…The CI+all-order method was used to accurately evaluate properties of atomic systems with two to four valence electrons [9][10][11][12][13][14][15][16], including superheavy elements No, Lr and Rf [17]. An advantage of this approach is an ability to include core correlations for all core shells together with the accurate description of the valence electronic correlations.…”

Blackbody radiation shift of the Ga+clock transition

“…The BBR shifts of all these ions were found to be small, with In + having the largest 300 K BBR shift of −0.017 Hz [15][16][17]. All of these BBR shifts were between 1 to 2 orders of magnitude smaller than the BBR shifts of other atoms and ions advanced as atomic frequency standards [7].…”