We report continuous-wave laser action in two oxide nanopowders doped with Ce 3ϩ and Pr 3ϩ ions. To our knowledge, these are the first observations of stimulated emission from electrically pumped random media in which scattering and distributed feedback scale lengths are much shorter than a wavelength. The continuous nature of the laser emission in small volumes ͑on the order of a cubic wavelength͒ of these low gain systems, and the absence of coherent speckle, provide compelling evidence that these results are mediated by strong Anderson localization of light.

Measurements of the linear polarization degree of the 5p 2 P 3/2 →8p 2 P j Ј transitions ( jЈϭ1/2,3/2) in atomic 87 Rb are reported. The radiative transitions are electric-dipole forbidden, but electric-quadrupole allowed. In addition, because of the relatively strong spin-orbit interaction in Rb, the p-p transitions can acquire a magnetic-dipole transition strength that may be a measurable fraction of the electric-quadrupole strength. The polarization measurements can generally provide a different and sensitive way to extract the relative transition strengths. We have measured the linear polarization degree of the 5p 2 P 3/2 →8p 2 P j Ј transitions over a wide range of Rb density. We report here observations of a different depolarization effect, whereby the measured polarization of the 5s 2 S 1/2 →5p 2 P 3/2 →8p 2 P 1/2 transition increases, while that for the 5s 2 S 1/2 →5p 2 P 3/2 →8p 2 P 3/2 transition decreases with increasing Rb density. The behavior is attributed to strong laser field effects associated with the 5s 2 S 1/2 →5p 2 P 3/2 resonance transition.

We describe a straightforward and highly visual experiment designed to demonstrate Raman scattering spectroscopy by measuring the vibrational energy spacing of nitrogen molecules in the liquid phase. Interpretation of the spectrum teaches the principles of elastic and inelastic light scattering and the intrinsic properties of molecules. The use of a pulsed Nd: YAG laser with high peak power leads to a plethora of nonlinear optical phenomena. The presence of highly visible stimulated Raman scattering greatly enhances the normal Raman-shifted signal, allowing for a more engaging laboratory experience in comparison to traditional Raman scattering experiments.

We report on the lifetime measurement of the 6 1Σg+(7,31) state of Na2 molecules, produced in a heat-pipe oven, using a time-resolved spectroscopic technique. The 6 1Σg+(7,31) level was populated by two-step two-color double resonance excitation via the intermediate A 1Σu+(8,30) state. The excitation scheme was done using two synchronized pulsed dye lasers pumped by a Nd:YAG laser operating at the second harmonics. The fluorescence emitted upon decay to the final state was measured using a time-correlated photon counting technique, as a function of argon pressure. From this, the radiative lifetime was extracted by extrapolating the plot to collision-free zero pressure. We also report the calculated radiative lifetimes of the Na2 6 1Σg+ ro-vibrational levels in the range of v = 0–200 with J = 1 and J = 31 using the LEVEL program for bound-bound and the BCONT program for bound-free transitions. Our calculations reveal the importance of the bound-free transitions on the lifetime calculations and a large difference of about a factor of three between the J = 1 and J = 31 for the v = 40 and v = 100, respectively, due to the wavefunction alternating between having predominantly inner and outer well amplitude.

An experimental investigation of the Cs 6s 2 S 1/2 → 6p 2 P 3/2 → 10s 2 S 1/2 double-resonance two-photon polarization spectrum has been made. In the investigation, a linear polarization degree was measured to extract the alignment depolarization cross section in the cesium 6p 2 P 3/2 level due to collisions between ground-level argon and excited 6p 2 P 3/2 cesium atoms over the Zeeman coherences. The spectra show strong depolarization of the Cs 6p 2 P 3/2 level. The measured alignment depolarization cross section value of 186 ͑58͒ Å 2 is in good agreement with the experiment and theoretical predictions.