A N Goncharov

Second-order Zeeman effect of theX−B transition in molecular iodine

Saturated absorption spectroscopy was applied to study the line shape of the molecular iodineX(ν″ = 0,J″ = 13,15) →B(ν′ = 43,J′ = 12, 16) transition (λ = 514.5 nm) in a transversal magnetic field as high as 0.51 T. The Zeeman structure of several hyperfine structure (hfs) components was completely resolved and a detailed study of the second-order Zeeman shift and splitting was made. The anisotropic Magnetic Susceptibility (MS) of the molecular iodine both in theB(43) (X′ = 7.3 ± 1 × 10−34 J/Oe2) and theX(0) [χ″ = (0.6 ± 1) × 10−34 J/Oe2] states as well as the isotropic MS difference [χ′0 −χ″o = (2 ± 0.2) × 10−34 J/Oe2] was measured.

Magneto-optical trap formed by elliptically polarised light waves for Mg atoms

We consider a magneto-optical trap (MOT) formed by elliptically polarised waves for 24Mg atoms on a closed optical 3P2 → 3D3 (λ = 383.8 nm) transition in the e – θ – configuration of the field. Compared with a known MOT formed by circularly polarised waves (σ+ – σ- configuration), the suggested configuration of the trap formed by fields of e – θ – configuration allows deeper sub-Doppler cooling of trapped 24Mg atoms, which cannot be implemented in a conventional trap formed by fields of σ+ – σ- configuration.

An optical frequency standard based on ultracold magnesium atoms

This paper presents the recent experimental results on development of an optical frequency standard based on ultra cold magnesium atoms with relative frequency uncertainty and long term stability at the level of / <10 . We stabilized the frequency of our clock laser system at 655 THz to narrow Ramsey fringes in a time separated laser fields interacting with cooled Mg atoms localized in a magneto-optical trap (MOT). The intercombination line S0→P1 was used as the reference for frequency stabilization. The results of stabilization were studied with femtosecond comb based on Ti:Sa laser. Optical frequency standards based on cooled and localized atoms play an important role in both fundamental research and various metrological and navigational applications. Alkaline-earth and alkaline-earth-like atoms such as Yb [1], Ca [2], Sr [3–5], Hg [6] and Mg [7, 8] are the main candidates to create frequency standards of a new generation. Today, Yb and Sr optical-lattices frequency standards demonstrate a relative instability and uncertainty of extremely low levels 10÷10 [1, 4]. Mg frequency standard at the moment much less developed compare to Sr and Yb optical standards. At the same time, magnesium atoms have some advantages compared to the other candidates in terms of the frequency standard. Thus, the blackbody radiation (BBR) shift of the clock transition for magnesium is much smaller than for Yb, Ca, Sr. The simplified level scheme of Mg atoms is shown at figure 1. Figure 1. Simplified term diagram of Mg atoms. Solid lines denote the cooling transitions with corresponding temperature limits, while dashed lines denote possible “clock” transitions, which can be used for laser frequency stabilization. MPLP-2016 IOP Publishing IOP Conf. Series: Journal of Physics: Conf. Series 793 (2017) 012008 doi:10.1088/1742-6596/793/1/012008 International Conference on Recent Trends in Physics 2016 (ICRTP2016) IOP Publishing Journal of Physics: Conference Series 755 (2016) 011001 doi:10.1088/1742-6596/755/1/011001 Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 The resonant strong transition S0→P1 is a very suitable for an effective laser cooling and trapping of Mg atoms in a magneto-optical trap (MOT) directly from a thermal atomic beam. The Mg S0→P1 transition natural width is only 31 Hz and it could be used to develop an optical frequency standard with high long term frequency stability. Strongly forbidden S0→P0 transition is of particular interest to develop an “optical lattice” standard with relative frequency uncertainty of 10÷10. To observe S0→P0 transition the magnetic-field-induced spectroscopy method could be used [9]. Despite a number of difficulties for deep cooling of Mg atoms down to a temperature less than 100 μK due to a large value of recoil energy, studies aimed at creating an optical frequency standard based on Mg atoms are carried out at the Institut für Quantenoptik, Hannover, Germany [7] and the Institute of Laser Physics, Novosibirsk, Russia [8] In our previous studies we localized a cloud of cooled Mg atoms in MOT and have observed narrow Ramsey resonances in time separated laser fields at the intercombination transition S0→P1 [8]. This paper presents preliminary results on a clock laser frequency stabilization using Ramsey resonances and a frequency stability measurements with a frequency comb generator based on a femtosecond Ti:Sa laser. A schematic diagram of Mg optical frequency standard is shown at figure 2. Figure 2. Simplified schematic of the experimental setup, showing the 914 nm Ti:Sa laser, the cavity with KNbO3 crystal for frequency doubling to the “clock” wavelength of 457 nm, the reference cavity for Ti:Sa laser linewidth preliminary narrowing, the zerodur cavity with a two pass acousto-optical modulator (AOM) for frequency stabilization and fine tuning of the clock laser frequency, the MOT with a detection system. The frequency of clock laser system was stabilized using a highly stable zerodur cavity and was tuned with the generator Agilent N5181A controlled AOM. A digital version of the third harmonic detection method is used to generate an error signal for frequency stabilization of the clock laser system to a central Ramsey fringe [10]. The four radio frequencies were generated with four channel DDS generator. These frequency were ∆1 = f0+∆/4, ∆-1 =f0–∆/4, ∆3 = f0+3∆/4, ∆-3 =f0–3∆/4, were ∆ is a value of the Ramsey fringes period, f0 = 80 MHz is a central frequency of AOM, that formed time separated pulses for cooled Mg atoms excitation. A calculated error signal dS=(S∆-3–3S∆-1+3S∆1–S∆3) MPLP-2016 IOP Publishing IOP Conf. Series: Journal of Physics: Conf. Series 793 (2017) 012008 doi:10.1088/1742-6596/793/1/012008

Spectroscopy of the Mg {sup 1}S{sub 0}-{sup 3}P{sub 1} intercombination transition in a luminescent cell with walls at room temperature

Absorption at the 1S0—3P1 intercombination transition in magnesium atoms is studied experimentally. The saturated absorption resonance of thermal magnesium atoms in a compact low-pressure absorption cell with walls at room temperature was recorded for the first time by using the spatial trapping of excited magnesium atoms in the detection region and the time separation of luminescence excitation and detection.