We precisely investigate the Zeeman and Paschen-Back effects of the hyperfine structure during the rubidium $5{\phantom{\rule{0.16em}{0ex}}}^{2}{S}_{1/2}\ensuremath{\rightarrow}5{\phantom{\rule{0.16em}{0ex}}}^{2}{D}_{5/2}$ two-photon transition. Owing to the high sensitivity of the
D state of atoms to a magnetic field, the splittings of the spectra of the
D state are sufficiently large in a weak magnetic field of
<10 G. We experimentally observe how in the hyperfine coupling in the
52D5/2 state is disrupted even in weak magnetic fields around 10 G and the energy levels are arranged according to their total angular momentum
J and nuclear spin
I. The transient of the spectra known as the Paschen-Back effect is observed even in a weak magnetic field with an order of magnitude of several tens of gauss. The results of theoretical calculations for energy shifts and transition intensities under a magnetic field are in quantitative agreement with the experimental results.
The optical spectroscopy and dynamics of three materials; Eu^3+:Y2SiO5, Pr^3+:Y2SiO5, and Tm^3+:Y2SiO5 that are of interest for application in persistent spectral holeburning optical memory and signal processing devices were investigated using linear and nonlinear spectroscopic techniques.Two-pulse photon echoes have been used to measure the homogeneous linewidths.The effects of instantaneous spectral diffusion were systematically studied to allow accurate determination of the optical resonance widths, and external magnetic fields were applied to characterize the effects of fluctuating nuclear spins of the host lattice on dephasing of the dopant ion.The 7F0 → 5D0 transition of 0.1% Eu^3+ in the two crystallographic sites of Y2SiO5 was studied using photon echoes.Using this material, we succeeded in measuring the narrowest optical resonance in a solid by shielding the crystal from stray electromagnetic fields and using sufficiently low laser power to minimize contributions from instantaneous diffusion.The homogeneous linewidths measured in a magnetic field of 100 G are 122 Hz (site 1) and 167 Hz (site 2).These widths are dominated by population decay, but up to 20 Hz is attributed to 89Y spin fluctuations which have been reduced by the applied magnetic field.Similar studies were performed to determine the contributions to the homogeneous linewidth of the 3H4(1) → 1D2(1) transition for both sites of 0.02% Pr^3+ in Y2SiO5.Linewidths of 2.1 kHz (site 1) and 0.85 kHz (site 2) were obtained with an applied magnetic field of 77 G.A significant contribution of 89Y nuclear spin fluctuations to the zero-field homogeneous linewidth was found.Optically detected nuclear magnetic resonance measurements determined the hyperfine structure of the 3H4 ground state for each site, and photon echo nuclear double resonance was used to determine the hyperfine levels of the lowest component of the 1D2 manifold. 3) 2.1? Ec,2S