Absolute frequency measurement of the7s2 1S0–7s

Abstract

Transition frequencies were determined for transitions in Ra in an atomic beam and for reference lines in Te2 molecules in a vapor cell. The absolute frequencies were calibrated against a GPS stabilized Rb-clock by means of an optical frequency comb. The 7s 2 1 S0(F = 1/2)-7s7p 1 P1(F = 3/2) transition in 225 Ra was determined to be 621 042 124(2) MHz. The measurements provide input for designing efficient and robust laser cooling of Ra atoms in preparation of a search for a permanent electric dipole moment in Ra isotopes. PACS numbers: 31.30.jp, 11.30.Er, 42.62.Fi, Radium (Ra) is the heaviest alkaline earth metal and it offers unique possibilities for measuring parity and time reversal symmetry violation. The particular atomic and nuclear [1][2][3][4][5][6][7][8] structure in Ra isotopes cause the largest enhancement for permanent electric dipole moments (EDMs) [9] in any atom. This arises from the close proximity of the 7s7p 3 P 1 and 7s6d3 D 2 states [1]. The exploitation of the enhancement from this 5 cm −1 separation requires precise knowledge of Ra atomic properties such as the absolute frequencies of transitions that are relevant for laser cooling and state manipulation (see Fig. 1). Many isotopes of Ra are available from radioactive sources such as 229 Th [10-13], or at online isotope production facilities such as ISOLDE, CERN, Switzerland [14,15].A sensitive search for EDMs requires efficient collection of the atoms in an optical trap because of the low abundance of Ra isotopes. A strategy for efficient laser cooling and trapping has been developed with the chemical homologue barium (Ba). Exploiting the strong 6s 2 1 S 0 -6s6p 1 P 1 transition [16,17] resulted in an efficiency of ∼1% for slowing and capturing Ba from an atomic beam, whereas capture efficiencies of below 10 −6 were reported for Ra when using the weak intercombination transition 7sThe optical spectrum of Ra was first studied by Rasmussen [18]. This identified Ra as an alkaline earth metal. Hyperfine splittings and isotope shifts were determined for the 7s 2 1 S 0 -7s7p 1,3 P 1 transitions by collinear laser spectroscopy [14,15] with intense Ra ion beams at ISOLDE, lifetimes of low lying states were determined in ANL, USA [9,19]; no absolute frequencies are quoted.Here we report on a laser spectroscopy measurement of the frequency of the strong 7s 2 1 S 0 -7s7p

Spectra of barium, radium, and element 120: Application of the combined correlation-potential, singles-doubles, and configuration-interactionab initiomethods

“…There are already a number of theoretical works devoted to studies of fundamental symmetries violations in radium [7,[9][10][11][12][13][14] and to the radium spectra, lifetimes, and hyperfine structure [15][16][17][18][19][20][21]. There are also recent measurements of a few transition frequencies and lifetimes [22][23][24]. In this work we use a recently-developed approach that combines the correlation potential, singlesdoubles coupled-cluster, and configuration interaction methods [25] to the radium spectra.…”

Parity and Time-Reversal Violation in Atomic Systems

“…Much experimental work is currently under way that promises significant improvements in the measurements in the near future, e.g., in Xe [140], YbF [141,142], TlF [143] and ThO [144][145][146][147]. New experiments are also in preparation designed to measure the EDM of Xe [148] and Fr [149] at CYRIC in Tohoku, Ra at KVI [150] and Argonne laboratory [151,152], and Rn at TRIUMF [153] (see also [154]). Very recently, the SrF molecule was successfully trapped and cooled, demonstrating the the ability of this technique, which can be applied to molecular EDM and PNC experiments [118,119].…”

Compilation of Spectroscopic Data of Radium (Ra I and Ra II)

“…With the advent of accelerator facilities, modern experimental methods to produce radium isotopes and to probe the atomic structure, more information is available on these spectra in the literature. At this juncture, we realized the need to update the information available on Ra atom and Ra ion and gathered it, which might be beneficial for various experiments that are in progress [10][11][12][13][14] and for the future experiments 15,16 with different physics motivations and for various fields of research. a) dammalapati.umakanth.a8@tohoku.ac.jp; Present address: Cyclotron and Radioisotope Center (CYRIC), Tohoku University, 6-3 Aramaki-aza Aoba, Aoba-ku, Miyagi 980-8578, Japan b) l.willmann@rug.nl About forty six years after Rasmussen's measurement of energy levels and wavelengths in Ra ion and Ra atom, furnace-absorption measurements of energy levels of the 7snp 1 P 0 1 (n = 13 − 52) series of neutral radium in the ultraviolet region were reported by Armstrong et al 17,18 .…”

“…At the University of Groningen, The Netherlands, with 229 Th (10 µCi) placed in an oven, 225 Ra neutral atomic beam was produced. Employing this thermal beam of Ra atoms, the absolute frequency of the strong electric dipole 7s 2 1 S 0 -7s7p 1 P 0 1 transition and weaker in-tercombination 7s 2 1 S 0 -7s7p 3 P 1 transition were reported with reference to a femtosecond optical frequency comb 12,40 . The uncertainty reported was 0.00006 cm −1 and 0.00013 cm −1 , respectively.…”