The CREMA collaboration is pursuing a measurement of the ground-state hyperfine splitting (HFS) in muonic hydrogen (\muμp) with 1 ppm accuracy by means of pulsed laser spectroscopy to determine the two-photon-exchange contribution with 2\times10^{-4}2×10−4 relative accuracy. In the proposed experiment, the \muμp atom undergoes a laser excitation from the singlet hyperfine state to the triplet hyperfine state, {then} is quenched back to the singlet state by an inelastic collision with a H_22 molecule. The resulting increase of kinetic energy after the collisional deexcitation is used as a signature of a successful laser transition between hyperfine states. In this paper, we calculate the combined probability that a \muμp atom initially in the singlet hyperfine state undergoes a laser excitation to the triplet state followed by a collisional-induced deexcitation back to the singlet state. This combined probability has been computed using the optical Bloch equations including the inelastic and elastic collisions. Omitting the decoherence effects caused by {the laser bandwidth and }collisions would overestimate the transition probability by more than a factor of {two in the experimental conditions. Moreover,} we also account for Doppler effects and provide the matrix element, the saturation fluence, the elastic and inelastic collision rates for the singlet and triplet states, and the resonance linewidth. This calculation thus quantifies one of the key unknowns of the HFS experiment, leading to a precise definition of the requirements for the laser system and to an optimization of the hydrogen gas target where \muμp is formed and the laser spectroscopy will occur.
We demonstrate a tunable external cavity tapered amplifier laser (ECTAL) using a narrowband interference filter as the wavelength discriminator. The laser is tunable over a wavelength range from 1006 to 1031 nm with an output power of ∼1 W. The amplified stimulated emission of the laser system is suppressed to better than 32 dB. The laser is applied to study the saturation spectroscopy on the R(39) 57-0 line of iodine molecule, which, to our best knowledge, is the first measurement of this line close to the dissociation limit. The linewidth of the a component is ∼2 MHz at the iodine vapor pressure of ∼11 Pa, and the pressure-broadening coefficient is ∼156 kHz/Pa. This laser system is also used for the injection seeding of a 1030 nm disk laser to perform hyperfine spectroscopy of muonic hydrogen. To reach a satisfactory condition for disk laser use, the ECTAL is successfully stabilized to the iodine Doppler-free spectroscopy of the P(26) 43-0 line near 515 nm, with continuous locking over 48 h.
We present experimental results on the sub-Doppler Rydberg spectroscopy of potassium in a hot cell and cold atoms, using two counterpropagating laser beams of 405 and 980 nm as an inverted ladder-type excitation configuration (4S 1/2-5P 3/2-nS 1/2 and nD 3/2,5/2). Such an inverted ladder-type scheme is predicted to be without the sub-Doppler electromagnetically induced transparency feature in a thermal ensemble under the weak-probe approximation. Instead, we utilize a strong probe field and successfully observe a transparency window with a width narrower than 50 MHz. Our all-order numerical simulation is in satisfactory agreement with the experimental results. This narrow linewidth allows us to measure the energy levels of the Rydberg levels from n = 20-70 with improved accuracy. The deduced ionization energy agrees with the previous measurements. Furthermore, the two-photon Rydberg excitation scheme was applied to the cold ensembles to study the ground-state atoms population decrease in the magneto-optical trap for various Rydberg states. Our experimental observations suggested two distinct regimes of the trap losses under different probe detuning conditions. While the far off-resonance case (p 0) can be described by the picture of dressed atom, the on-resonance case (p ∼ 0) reveals more interesting results. The higher Rydberg states suffer larger trap loss. Besides, even with similar level energies, the excitation to nD states result in faster escape of the ground-state atom from trap than nearby nS states.
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