PACS. 32.10.Fn -Fine and hyperfine structure. PACS. 42.50.Gy -Effects of atomic coherence on propagation, absorption, and amplification of light. PACS. 42.50.-p -Quantum optics.Abstract. -We use the phenomenon of electromagnetically-induced transparency in a threelevel atomic system for hyperfine spectroscopy of upper states that are not directly coupled to the ground state. The three levels form a ladder system: the probe laser couples the ground state to the lower excited state, while the control laser couples the two upper states. As the frequency of the control laser is scanned, the probe absorption shows transparency peaks whenever the control laser is resonant with a hyperfine level of the upper state. As an illustration of the technique, we measure hyperfine structure in the 7S 1/2 states of 85 Rb and 87 Rb, and obtain an improvement of more than an order of magnitude over previous values.The use of coherent-control techniques in three-level systems is now an important tool for modifying the absorption properties of a weak probe laser [1,2,3]. For example, in the phenomenon of electromagnetically induced transparency (EIT), an initially absorbing medium is made transparent to a probe beam when a strong control laser is switched on [4,5]. EIT techniques have several practical applications in probe amplification [6], lasing without inversion [7], and suppression of spontaneous emission [3,8,9,10]. Experimental observations of EIT have been mainly done using alkali atoms (such as Rb and Cs), where the transitions have strong oscillator strengths and can be accessed with low-cost tunable diode lasers.In this paper, we use the phenomenon of EIT in a novel application, namely high-resolution spectroscopy of hyperfine structure in excited states. The experiments are done in a ladder system, where the control laser drives the upper transition and the probe laser measures absorption on the lower transition. In normal EIT experiments, the frequency of the probe laser is scanned while the frequency of the control laser is kept fixed. By contrast, in our technique, it is the frequency of the control laser that is scanned while the probe laser remains locked on resonance. The probe-absorption signal then shows transparency peaks every time the control laser comes into resonance with a hyperfine level of the excited state.Measurement of hyperfine structure in excited states is important because these states are used in diverse experiments ranging from atomic signatures of parity non-conservation (PNC)
We demonstrate a technique to measure hyperfine structure using a frequency-stabilized diode laser and an acousto-optic modulator locked to the frequency difference between two hyperfine peaks. We use this technique to measure hyperfine intervals in the 5P 3/2 state of 85 Rb and obtain a precision of 20 kHz. We extract values for the magnetic-dipole coupling constant A = 25.038(5) MHz and the electric-quadrupole coupling constant B = 26.011(22) MHz. These values are a significant improvement over previous results.PACS numbers: 32.10.Fn,42.55.Px,42.62.Fi The use of tunable diode lasers has revolutionized the field of atomic physics [1] and particularly laser spectroscopy. The D-lines of most alkali atoms can be conveniently accessed using diode lasers. Therefore, they have been used extensively on alkali atoms as tools for pumpprobe spectroscopy, optical-pumping experiments, quantum optics, and the study of three-level systems. They find widespread use in experiments on laser cooling and Bose-Einstein condensation of alkali atoms. They have also been proposed as potential low-cost alternatives for optical-frequency standards [2]. We have been exploring the use of diode lasers for precise measurements of hyperfine intervals in the excited state of alkali atoms. Precise knowledge of hyperfine intervals provides valuable information about the structure of the nucleus (nuclear deformation) and its influence on atomic wavefunctions [3,4]. The exact knowledge of atomic wavefunctions is particularly important in alkali atoms because of their use in experiments such as atomic signatures of parity violation [5].
We have successfully loaded a magneto-optic trap for Yb atoms from a thermal source without the use of a Zeeman slower. The source is placed close to the trapping region so that it provides a large flux of atoms that can be cooled and captured. The atoms are cooled on the 1 S 0 ↔ 1 P 1 transition at 398.8 nm. We have loaded all seven stable isotopes of Yb into the trap. For the most abundant isotope ( 174 Yb), we load more than 10 7 atoms into the trap within 1 s. For the rarest isotope ( 168 Yb) with a natural abundance of only 0.13%, we still load about 4 × 10 5 atoms into the trap. We find that the trap population is maximized near a detuning of −1.5Γ and field gradient of 75 G/cm. 32.80.Pj,42.50.Vk
PACS. 32.30.Jc -Visible and ultraviolet spectra. PACS. 32.10.Fn -Fine and hyperfine structure. PACS. 42.62.Fi -Laser spectroscopy.Abstract. -We demonstrate a technique for frequency measurements of UV transitions with sub-MHz precision. The frequency is measured using a ring-cavity resonator whose length is calibrated against a reference laser locked to the D2 line of 87 Rb. We have used this to measure the 398.8 nm 1 S0 ↔ 1 P 1 line of atomic Yb. We report isotope shifts of all the seven stable isotopes, including the rarest isotope 168 Yb. We have been able to resolve the overlapping 173 Yb(F = 3/2) and 172 Yb transitions for the first time. We also obtain highprecision measurements of excited-state hyperfine structure in the odd isotopes, 171 Yb and 173 Yb. The measurements resolve several discrepancies among earlier measurements.Precise measurements of the frequencies of atomic transitions are an important tool in expanding our knowledge of physics. For example, precise measurement of the D 1 line in Cs [1] combined with an atom-interferometric measurement of the photon recoil shift [2] could lead to a more accurate determination of the fine-structure constant α. In addition, hyperfinestructure and isotope-shift measurements in atomic lines can help in fine-tuning the atomic wavefunction, particularly due to contributions from nuclear interactions. This is important when comparing theoretical calculations with experimental data in atomic studies of parity violation [3]. The most precise optical frequency measurements to date have been done using the recently developed frequency-comb method with mode-locked lasers [1], with errors below 100 kHz being reported. However, to the best of our knowledge, this technique has not yet been applied to UV spectroscopy, which relies on older and less-accurate techniques.In this Letter, we present the most comprehensive study of the 398.8 nm 1 S 0 ↔ 1 P 1 line of atomic Yb. Yb (Z=70) is an attractive candidate for studying atomic parity violation [4] and the search for a permanent electric-dipole moment in atoms [5]. Laser-cooled Yb has also been proposed for frequency-standards applications [6]. The 1 S 0 ↔ 1 P 1 line is widely used in laser-cooling experiments [5,7]. Over the years, there has been much interest in this line, and its isotopic and hyperfine components have been measured using a variety of techniques -level-crossing and anti-crossing spectroscopy [8,9,10], Fabry-Perot cavity [11], saturatedabsorption spectroscopy [12], photon-burst spectroscopy [13], and most recently using optical
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