Neodymium (Nd 3+ ) ions in mixed yttrofluorite crystals were excited by Y 3 Al 5 O 12 :Nd 3+ laser radiation. Luminescence spectra of these ions were recorded in 5x10 –6 sec after a delay time (relative to a short excitation pulse), which was varied within the range from 3 × 10 –5 to 2 × 10 –3 sec. The spectra recorded during the initial stages of the decay of the 4 F 3/2 metastable state were quite different from the spectra recorded under nonselective excitation conditions. The selectively excited spectra varied with time because of the migration of energy between metastable states but this migration was completed in a time of the order of 10 –3 sec at T = 300°K when the concentration of NdF 3 was 1 wt.%. The results indicated a correlation between the spectra of the energy levels of Nd 3+ in yttrofluorite crystals and structural disorder.Neodymium (Nd 3+ ) ions in mixed yttrofluorite crystals were excited by Y 3 Al 5 O 12 :Nd 3+ laser radiation. Luminescence spectra of these ions were recorded in 5x10 –6 sec after a delay time (relative to a short excitation pulse), which was varied within the range from 3 × 10 –5 to 2 × 10 –3 sec. The spectra recorded during the initial stages of the decay of the 4 F 3/2 metastable state were quite different from the spectra recorded under nonselective excitation conditions. The selectively excited spectra varied with time because of the migration of energy between metastable states but this migration was completed in a time of the order of 10 –3 sec at T = 300°K when the concentration of NdF 3 was 1 wt.%. The results indicated a correlation between the spectra of the energy levels of Nd 3+ in yttrofluorite crystals and structural disorder.

Soviet Journal of Quantum ElectronicsMay 31, 19775 citations

Collective excitations and confinement in the excitation spectra of the spinless fermion model on a ladder

Kenji Yonemitsu

Intrachain and interchain local charge-transfer excitation spectra and the single-particle density of states are calculated in the spinless fermion model on a ladder with varying intrachain nearest-neighbor repulsion and interchain transfer integral at and near half filling by using the finite-temperature density-matrix renormalization-group method. Collective excitations are found to govern the low-energy intrachain spectra, while only individual local excitations are present in the interchain spectra. For strong intrachain repulsion, the low-energy motion of fermions is confined within a chain. The interchain motion of fermions is not bandlike but incoherent. As a consequence, the low-energy intrachain spectra are sensitive at half filling to the interchain transfer integral that weakens the density-density correlation along the chains. Similarly, the low-energy intrachain spectra are sensitive near half filling to the chemical potential that reduces the effect of the umklapp process. Similarities are pointed out between these findings and the experimentally observed, optical conductivity spectra in the quasi-one-dimensional organic conductors $(\mathrm{TMTSF}{)}_{2}X.$ Intrachain and interchain local charge-transfer excitation spectra and the single-particle density of states are calculated in the spinless fermion model on a ladder with varying intrachain nearest-neighbor repulsion and interchain transfer integral at and near half filling by using the finite-temperature density-matrix renormalization-group method. Collective excitations are found to govern the low-energy intrachain spectra, while only individual local excitations are present in the interchain spectra. For strong intrachain repulsion, the low-energy motion of fermions is confined within a chain. The interchain motion of fermions is not bandlike but incoherent. As a consequence, the low-energy intrachain spectra are sensitive at half filling to the interchain transfer integral that weakens the density-density correlation along the chains. Similarly, the low-energy intrachain spectra are sensitive near half filling to the chemical potential that reduces the effect of the umklapp process. Similarities are pointed out between these findings and the experimentally observed, optical conductivity spectra in the quasi-one-dimensional organic conductors $(\mathrm{TMTSF}{)}_{2}X.$

Physical review. B, Condensed matterJul 31, 20020 citations

Excitation of Atoms

Igor I Sobel'man

Elsevier eBooksJan 1, 19728 citations

Spin excitation spectra of spin–orbit coupled bosons in an optical lattice

Ruo-Yan Li, Liang He, Qing Sun +2 more

Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin–orbit coupling in a deep square optical lattice using the spin-wave theory. We find that, while the excitation spectrum of the vortex crystal phase is gapless with a linear dispersion in the vicinity of the minimum point, the spectra of the commensurate spiral spin phase and the skyrmion crystal phase are gapped. Significantly, the spin fluctuations strongly destabilize the classical ground state of the skyrmion phase with the appearance of an imaginary part in the eigenfrequencies of spin excitations. Such features of the spin excitation spectra provide further insights into the exotic spin phases.Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin–orbit coupling in a deep square optical lattice using the spin-wave theory. We find that, while the excitation spectrum of the vortex crystal phase is gapless with a linear dispersion in the vicinity of the minimum point, the spectra of the commensurate spiral spin phase and the skyrmion crystal phase are gapped. Significantly, the spin fluctuations strongly destabilize the classical ground state of the skyrmion phase with the appearance of an imaginary part in the eigenfrequencies of spin excitations. Such features of the spin excitation spectra provide further insights into the exotic spin phases.

arXiv:1407.4172Chinese Physics BApr 30, 20152 citations

Atomic excitation and spectral line broadening

Leonid A. Vainshtein, Igor I Sobel'man, E. A. Iukov

Moscow Izdatel NaukaJan 1, 197911 citations

(\mathrm{TMTSF}{)}_{2}X.