Raman scattering is observed in MgO microcrystals with three different particle sizes (105, 103, and 102 Å). The second-order Raman lines in the bulk crystals of MgO disappear in all the microcrystals, while new peaks emerge at 280, 446, and 1088 cm−1 except for specimen prepared by grinding a large single crystal. Raman lines with lower frequencies, which are enhanced with decrease of the particle size, are discussed as due to the first-order Raman scattering forbidden in the bulk crystals. The assignment is confirmed in terms of photon density of states in microcrystals. Another line with the highest frequency is coincident with a previously reported Raman line whose origin has been attributed to a surface phonon mode.
High resolution spectrum of the B 1Π–X 1Σ+ transition of the NaRb molecule was measured with the technique of the Doppler-free laser polarization spectroscopy. Molecular constants of the B 1Π(v=0–12) and X 1Σ+(v=0–6) states of 23Na85Rb were determined. The energy levels of the B 1Π state were found to present many irregularities due to perturbations. The resonance fluorescence spectrum following an excitation to a strongly perturbed level was measured. The fluorescence to the (1)3Σ+ state, which consists of discrete lines followed by a continuum band, was observed in addition to the fluorescence lines to rovibrational levels of the X 1Σ+ state. The perturbing state to the B 1Π(v=8,J=15–21) levels is identified as the (1)3Π state by comparing the observed fluorescence spectra with the selection rules for perturbations and radiative transitions. The dissociation limit of the (1)3Σ+ state, which separates into the Na(3s2S1/2)+Rb(5s2S1/2) atoms, was deduced from the spectrum. The dissociation energies of the X 1Σ+, (1)3Σ+, and B 1Π states were determined to be 5030±2, 182±2, and 1319±2 cm−1, respectively.
We have succeeded in magneto-optical trapping of Yb atoms decelerated by a Zeeman slower method. The number of the trapped atoms is more than about 1.3ϫ10 6 measured by light absorption. We have found the evidence of the branching from the 1 P 1 excited state to triplet states, and determined the lower limit on the branching ratio to be 1.2ϫ10 Ϫ7 .
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