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If there is explicit violation of baryon plus lepton number at some energy scale, then the electroweak theory depends upon a θ-angle. Due to a singular integration over small scale size instantons, this θ -dependence is sensitive to very high momentum scales. Assuming that there is no new physics between the electroweak and Planck scales, for an electroweak axion the energy difference between the vacuum at θ≠0, and that at θ=0, is of the correct order of magnitude to be the dark energy observed in the present epoch. 相似文献
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J. Pisarska M. Sołtys L. Żur W. A. Pisarski C. K. Jayasankar 《Applied physics. B, Lasers and optics》2014,116(4):837-845
Excitation and luminescence properties of Eu3+, Tb3+ and Er3+ ions in lead phosphate glasses have been studied. From excitation spectra of Eu3+ ions, the electron–phonon coupling strength and phonon energy of the glass host were calculated and compared to that obtained by Raman spectroscopy. Main intense and long-lived luminescence bands are related to the 5D0–7F2 (red) transition of Eu3+, the 5D4–7F5 (green) transition of Tb3+ and the 4I13/2–4I15/2 (near-infrared) transition of Er3+. The critical transfer distances, the donor–acceptor interaction parameters and the energy transfer probabilities were calculated using the fitting of the luminescence decay curves from 5D0 (Eu3+), 5D4 (Tb3+) and 4I13/2 (Er3+) excited states. The energy transfer probabilities for Eu3+ (5D0), Tb3+ (5D4) and Er3+ (4I13/2) are relatively small, which indicates low self-quenching luminescence of rare earth ions in lead phosphate glasses. 相似文献
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Lead phosphate glasses containing Eu(3+) and Dy(3+) have been studied. Local structure was verified using Fourier transform (FT)-IR spectroscopy. Emission bands of Eu(3+) and Dy(3+) ions in lead phosphate glasses are observed in the visible spectral range, which correspond to 5D0→7F(J) (J=0,1,2,4) and 4F(9/2)→6H(J/2) (J=15,13,11) transitions, respectively. Shorter luminescence decays from excited states of Eu(3+) and Dy(3+0 are due to the presence of PbO in phosphate glass. 相似文献
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W.A. Pisarski J. Pisarska M. M?czka 《Journal of Physics and Chemistry of Solids》2006,67(12):2452-2457
New multicomponent lead borate based glasses with various PbO/B2O3 weight ratio were prepared. The glass samples were analyzed in detail by using Raman and IR absorption spectroscopy. Optical properties of Eu3+ ions have been investigated in lead borate based systems, in which PbO/B2O3 weight ratios were changed from 1:2 to 8:1 in glass composition. The values of the phonon energy of the host and 5D0 lifetime of Eu3+ decrease, whereas absorption and emission intensities, as well as bonding parameter increase with increasing PbO concentration. Additionally, spectral lines are shifted in direction to the lower frequency region. Non-monotonic dependence of the fluorescence intensity ratio R (5D0-7F2/5D0-7F1) upon PbO/B2O3 content has been observed in contrast to bonding parameter that is also non-linear but monotonic. Some structural and spectroscopic aspects for Eu-doped lead borate based glasses are presented. 相似文献
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Wojciech A. Pisarski Joanna Pisarska ?ukasz Grobelny Witold Ryba-Romanowski 《Journal of luminescence》2011,131(4):649-652
Ln-doped oxychloride lead borate glasses were studied using luminescence spectroscopy. Rare earth ions were limited to trivalent Pr3+, Tm3+, Eu3+ and Er3+. Luminescence spectra were registered, which correspond to 3P0-3H4 and 1D2-3H4 transitions of Pr3+, 1G4-3H5 and 1G4-3F4 transitions of Tm3+, 5D0-7FJ (J=0, 1, 2, 3, 4) transitions of Eu3+ and 4S3/2,2H11/2-4I15/2 and 4I13/2-4I15/2 transitions of Er3+. Luminescence decays from the excited states of Ln3+ ions were analyzed in detail. The experimental results indicate that relatively high phonon energy of the host gives important contribution to the excited state relaxation of rare earth ions. 相似文献
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