| 1. |
- Basiev, T. T., et al.
(författare)
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Pre-selection of optical transitions in rare-earth ions in crystals perspective for quantum information processing
- 2012
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 59:2, s. 166-178
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Tidskriftsartikel (refereegranskat)abstract
- A systematic analysis of decoherence rates due to electron-phonon interactions for optical transitions of rare-earth dopant ions in crystals is presented in the frame of the point charge model. For this model, the large value of any one of the matrix elements of the unit tensor operator U((k)) of rank k for transitions within the 4f-electronic configuration, viz. U2, U4 or U6, is enough to ensure the strong optical transition between different levels, while the Stark-Stark transitions within the multiplet can be characterized by the matrix element U2 alone, the influence of elements U4, U6 being of much smaller order of magnitude and neglected. The circumstance that exactly such Stark-Stark transitions within the multiplet define the efficiency of electron-phonon interaction and, consequently, the decoherence rate (except for the case of lowest, less than approximately 2-4 K, temperatures), enables selection of optical transitions which are strong enough and at the same time are characterized by relatively small decoherence rates. Correspondingly, these optical transitions, provided that they lie in an appropriate spectral range and the gap to the nearest neighboring energy level is large enough (>500 cm(-1)) to prevent eventual fast phonon-assisted relaxation, should be considered as prospective for subsequent use in quantum informatics processing and communication. The list of such pre-selected transitions is given; the applicability area and limitations of our approach are discussed.
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| 2. |
- Blagoveshchenskaya, N.F., Kornienko, V.A., Borisova, T.D., Thidé, B., Kosch, M.J., Rietveld, M.T., Mishin, E.V., Luk'yanova, R.Y. and Troshichev, O.A.
(författare)
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Ionospheric HF pump wave triggering of local auroral activation.
- 2001
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Ingår i: Journal of Geophysical Research. ; 106, s. 29071-29089
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Tidskriftsartikel (refereegranskat)abstract
- Experimental results from ionospheric HF pumping experiments in the nightside auroral E region above Tromso are reported. We found intriguing evidence that a modification of the ionosphere-magnetosphere coupling, due to the effects of powerful HF waves be
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| 3. |
- Blagoveshchenskaya, N.F., Kornienko, V.A., Rietveld, M.T., Thidé, B., Brekke, A., Moskvin, I.V., Nodrachev, S.
(författare)
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Stimulated emissions around second harmonic of Tromsø heater frequency observed by long-distance diagnostic HF tools
- 1998
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Ingår i: Geophysical Research Letters. ; 25, s. 863-876
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Blagoveshchenskaya, N. F., et al.
(författare)
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Heater-induced phenomena in a coupled ionosphere-magnetosphere system
- 2006
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Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 38:11, s. 2495-2502
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Tidskriftsartikel (refereegranskat)abstract
- Experimental results from HF pumping experiments in the nightside auroral E and F region are reported. The experiments were carried out by the use of the EISCAT HF heating facility located near Tromso, Norway, allowing HF pumping the ionosphere in a near magnetic field-aligned direction. We present experimental results from multi-instrument observations related to heater-induced phenomena in a coupled ionosphere-magnetosphere system. The following results have been observed on different occasions: a reverberation effect in scattered signals observed simultaneously on two diagnostic paths which is an indication of Alfven wave generation. This phenomenon was seen under specific disturbed background geophysical conditions, namely, a high electron density in the F region up to 8 MHz produced by soft electron precipitation from the magnetosphere along with low electron density in lower ionosphere; increased ionospheric electric fields; ion outflows from the ionosphere. On another occasion a magnetospheric response to heater turning on and off was found from magnetic pulsation observations over a frequency range up to 5 Hz (the upper frequency limit of the sensitive magnetometer at Kilpisjarvi, located near Tromso). The response manifests itself about 1 min after the heater is turned on and off. Other results have shown the modification of a natural auroral arc and local spiral-like formation. It is thought that a local heater-driven current system is formed. An interesting feature is the generation of the heater-induced ion outflows from the ionosphere. They are observed in night hours under both quiet and disturbed magnetic conditions.
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| 5. |
- Blagoveshchenskaya, N. F., et al.
(författare)
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Artificial field-aligned irregularities in the nightside auroral ionosphere
- 2006
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Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 38:11, s. 2503-2510
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Tidskriftsartikel (refereegranskat)abstract
- Experimental results from two Tromso HF heating experiments in the nightside high latitudinal F region are examined. Bi-static scatter measurements of HF diagnostic signals were carried out on the London-Tromso-St. Petersburg and Pori-Tromso-St. Petersburg paths using a Doppler spectral method. The properties and behaviour of artificial field-aligned small-scale irregularities (striations) in the nightside high latitudinal F-region in course of the Tromso ionospheric modification experiments are studied. Experimental studies have been performed by the use of phased array I with a beamwidth of 6 degrees instead of 12-14 degrees in phased array 2, more often used in Tromso ionospheric modification experiments. The comparison between two experiments carried out in the same background geophysical conditions, shows the strongest striations in the field-aligned position of the heater beam. Possible explanation for this angular dependence is self-focusing of HF pump waves on striations causing the energy to be distributed asymmetrically. A principal question related to HF heating experiments is how is the disturbed auroral ionosphere modified. The results obtained on two paths simultaneously have shown that the strong heater-induced striations were observed along with natural ones. Velocities of heater-induced striations were quite different at different parts of the heated volume. It is suggested that the heater-induced striations can be grouped in two patches at different heights possibly due to the temperature-gradient-driven instability.
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