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  • 1
    Electronic Resource
    Electronic Resource
    Diode-laser radiation absorption of CF2Cl2 around 921 cm−1 in a supersonic jet (1982)
    Springer
    Applied physics 29 (1982), S. 269-272 
    Details
    ISSN: 1432-0649
    Keywords: 33
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract With a diode laser we have studied the spectral region around 921 cm−1 of the CF2Cl2 molecule cooled in a free jet. Accurate studies of the intensity of two vibrorotational bands have enabled us to determine their assignment. In addition, the rotational structure has been partially resolved, and approximate fitting parameters have been deduced. The simultaneous use of a diode laser and a free jet has proved to be useful in correctly identifying the origin of the absorption bands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689186
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  • 2
    Electronic Resource
    Electronic Resource
    Absorption lineshape ofF A centres in alkali halides (1988)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 10 (1988), S. 693-708 
    Details
    ISSN: 0392-6737
    Keywords: Impurity and defect absorption in solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono state studiate per la prima volta le forme di riga delle bande di assorbimento dei centriF A in alogenuri alcalini. Il nuovo metodo usato per questa indagine è basato sulla determinazione attraverso misure di luminescenza della sovrapposizione fra le bandeF A1 eF A2 . I risultati sperimentali sono stati confrontati con i valori dedotti da bandeF A teoriche di diverse forme. La forma di riga dell'assorbimento a bassa temperatura, sia per i centriF A (I) in KCl: Na+ sia per i centriF A (II) in KCl: Li+ e RbCl: Li+, è approssimata molto meglio da una somma di due curve Lorentziane che da quella di due bande Gaussiane o Poissoniane. Questo risultato rivela una differenza imprevista rispetto ai centriF, il cui assorbimento ha una forma di riga Poissoniana alle stesse temperature.
    Abstract: Резюме Впервые исследуются формы линий зон поглощения дляF A центров в щелочно-галоидных соединениях. Предлагается новый метод исследования. Этот метод основан на определении перекрытия междуF A иF A2 зонами из измерений люминесценции. Экспериментальные результаты сравниваются с вычисленными величинами, полученными из теоретическихF A зон различной формы. ДляF A (I) центров в KCl: Na+ иF A (II) центров в KCl: Li+ и RbCl: Li+ форма линии поглощения при низких температурах оказывается ближе к сумме двух Лоренцевых кривых, а не двух Гауссовых или Пуассоновых зон. Этот результат обнаруживает неожиданное отличие отF центров, форма линии поглощения которых, как известно, представляет Пуассонову кривую при тех же температурах.
    Notes: Summary The lineshapes of the absorption bands ofF A centres in alkali halides have been studied for the first time. The new method used for this investigation is based on the determination of the overlap between theF A1 andF A2 bands from luminescence measurements. The experimental results have been compared with calculated values deduced from the theoreticalF A bands of different shapes. For bothF A (I) centres in KCl: Na+ andF A (II) centres in KCl: Li+ and RbCl: Li+ the absorption lineshape at low temperature is much closer to a sum of two Lorentzian curves than that of two Gaussian or Poissonian bands. This result shows an unexpected difference with theF centres, whose absorption lineshape is known to be Poissonian at the same temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02451107
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  • 3
    Electronic Resource
    Electronic Resource
    Spin-orbit coupling, spin-lattice relaxation, and spin-memory studies ofF-center-molecular-ion pairs in alkali halides (1993)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 15 (1993), S. 207-228 
    Details
    ISSN: 0392-6737
    Keywords: Magnetooptical effects ; Insulators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The spin-orbit parameter Δ, spin-lattice relaxation timeT 1, and spin-mixing parameter ɛ ofF H(OH−) andF H(CN−) centers in several alkali halides have been studied with magnetic circular dichroism at ∼2 K. A close comparison of the experimental results before and after optically induced association of theF center with the molecular ion has been made. In crystals of NaCl structure the negative spin-orbit parameter Δ changes little betweenF andF H centers in the same host. For CsCl and CsBr two values of Δ have been derived forF H(CN−) centers with axis parallel or perpendicular to the magnetic field. In all studied systems, the spin-lattice relaxation timeT 1 is already shorter before aggregation compared toF formation. The spin-mixing parameter ɛ decreases slightly forF H(OH−) compared toF centers, while it increases drastically forF H(CN−) defects and reaches its maximum possible value ɛ=0.5 in cesium halides. First attempts to interpret these magneto-optical results will be presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02456904
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  • 4
    Electronic Resource
    Electronic Resource
    Direct determination of site symmetry forF A centres in alkali halides (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 411-424 
    Details
    ISSN: 0392-6737
    Keywords: Solid alkali halides ; Optical rotatory power ; Impurity and defect absorption in solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The evaluation of site symmetry distortion for an impurity ion in cubic crystals is a problem which obtained attention from a number of investigators during the last decade. So far, all approaches were based on multi-parameter fittings of the experimental results by some theoretical curves. A new technique, described in this paper, makes it possible to obtain the site symmetry distortion parameter in a straightforward fashion directly from the experimental data. The method is based on precise measurements of the light polarization azimuth for a beam transmitted by a crystal with reorienting centres. results are reported forF A (Li) centres in KCl and RbCl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457343
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  • 5
    Electronic Resource
    Electronic Resource
    Revisited vibronic model for Li+ ion and F A (Li) centre in alkali halides (1991)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 1399-1421 
    Details
    ISSN: 0392-6737
    Keywords: Impurity and defect absorption in solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The controversial far-infrared optical absorption in Li-doped alkali halides is now attributed to transitions between the low-lying energy levels of an anharmonic oscillator composed of three halogen-ion pairs centred at the cation site which vibrate in theT 1u ungerade mode. This oscillator is electronically coupled to the impurity dragging it into rotation over 〈111〉 sites. Several experimental features derive simply from our model such as the absence of any clear-cut lithium-isotope effect and the low-frequency range. The capital effect of an F centre at a 〈001〉 nearest-neighbour (nn) site is to reduce the dimensionality of vibration forcing the impurity to rotate in the perpendicular (001)-plane. This upgrades the optical frequency in proportion to (3/2)1/2 and shrinks the off-centre displacement. We finally show that recent computer-simulation data on Li-doped alkali halides provide a solid ground for regarding the Li off-centredness as a pseudo-Jahn-Teller phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457128
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic circular dichroism in the luminescence ofF andF A centres in alkali halides (1990)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 12 (1990), S. 117-130 
    Details
    ISSN: 0392-6737
    Keywords: Magneto-optical effects ; Solid alkali halides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Gli effetti di dicroismo magnetico circolare hanno costituito in passato un ottimo mezzo per chiarire il ciclo ottico dei centriF in alogenuri alcalini e la natura dello stato eccitato rilassato. Abbiamo usato tale tecnica per studiare la debole doppia emissioneF trovata recentemente in NaI e la luminescenza dei centriF edF A (di tipo I e II) in KCl. Si è trovato che l'emissioneF a minore energia in NaI e l'emissioneF A (I) in KCl∶Na+ si comportano come la ben nota emissione dei centriF, il che conferma l'attribuzione di tale luminescenza in NaI allo stato eccitato rilassato normale. L'emissioneF a energia maggiore in NaI e l'emissioneF A (II) in KCl∶Li+ mostrano un comportamento completamente diverso. I dati sperimentali sono stati confrontati con la teoria vibronica di Ham e Grevsmuhl dello stato eccitato rilassato.
    Abstract: Резюме Магнитный круговой дихроизм ранее применялся как инструмент для выяснения оптического циклаF центров в щелочных галогенидах и природы релаксирующего возбужденного состояния. В этой работе мы используем эту технику для исследования слабого двойного F излучения, обнаруженного недавно в NaI и при люминесценцииF иF A центров (типа I и типа II) в KCl. Мы обнаружили, что длинноволновоеF излучения в NaI иF A (I) излучение в KCl∶Na+ ведет себя как хорошо известное излучениеF центров, что подтверждает приписывание вышеуказанной люминесценции в NaI нормальному релаксирующему возбужденному состоянию. Полностью отличное поведение обнаруживает коротковолновоеF излучение в NaI иF A (II) излучение в KCl∶Li+. Полученные экспериментальные данные сравниваются с вибрационной теорией Гама и Гревсмула для релаксирующего возбужденного состояния.
    Notes: Summary The magnetic circular dichroism has been in the past an excellent tool to clarify the optical cycle of theF centres in alkali halides and the nature of the relaxed excited state. We have used such technique to study the weak doubleF emission found recently in NaI and the luminescence ofF andF A centres (of both type I and II) in KCl. We have found that the long-wavelengthF emission in NaI and theF A (I) emission in KCl∶Na+ behave like the well-known emission of theF centres, confirming the attribution of the above luminescence in NaI to the normal relaxed excited state. A completely different behaviour is displayed by the short-wavelengthF emission in NaI and by theF A (II) emission in KCl∶Li+. The experimental data have been compared with the Ham and Grevsmuhl vibronic theory of the relaxed excited state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02453031
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  • 7
    Electronic Resource
    Electronic Resource
    Detailed model of the photostimulated realignment ofF FA centres in KCl:Li+ (1987)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 9 (1987), S. 1105-1114 
    Details
    ISSN: 0392-6737
    Keywords: Impurity and defect absorption in solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto La riorientazione fotostimolata dei centriF A in KCl:Li+ è descritta con un modello semplice che tiene conto dell’angolo di disallineamento e della sovrapposizione delle code delle due bande di assorbimento. Con questo modello abbiamo interpretato la dipendenza dell’intensità di luminescenza dalla polarizzazione della luce di eccitazione. Il fitting dei dati sperimentali dà un angolo di off-axis di circa 5° ed una sovrapposizione delle bande maggiore di quella prevista per curve di tipo gaussiano.
    Abstract: Резюме С помощью простой модели описывается фотостимулированная переориентацияF A центров в KCl:Li+. Эта модель учитывает угловое удаление центров от оси и перекрытие хвостов двух зон поглощения. С помощью этой модели мы интерпретируем зависимость интенсивности люминесценции от поляризации возбуждающего пучка. Подгонка экспериментальных данных дает угловое удаление от оси порядка 5° и большее перекрытие зон, чем было предсказано для гауссовых форм линий.
    Notes: Summary The photostimulated reorientation of theF A centres in KCl:Li+ is described by a simple model that takes into account the off-axis angle of the centres and the overlapping of the tails of the two absorption bands. With this model we have interpreted the dependence of the luminescence intensity on the polarization of the exciting beam. The fitting of the experimental data gives an off-axis angle of approximately 5° and an overlapping of the bands larger than that predicted for Gaussian line shapes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02451095
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic circular dichroism in the absorption of theF A centre in KCl doped with Li and Na (1990)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 12 (1990), S. 995-1003 
    Details
    ISSN: 0392-6737
    Keywords: Magneto-optical effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The spin-orbit structure ofF A centres in KCl:Li and KCl:Na have been studied by means of the magnetic circular dichroism. Due to theirC 4V symmetry theF A centres have two different spin-orbit parameters, Δ‖ and Δ⊥, which only in the KCl:Li case follow the relation: Δ‖ 〈 ΔF 〈 Δ⊥ as expected from the theory. For a close comparison we have also reported our measurement of the spin-orbit coupling ofF centre in KCl. The spin-orbit parameters of theF andF A centres have been determined using the method of moment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02453045
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  • 9
    Electronic Resource
    Electronic Resource
    A review of experiments and theory for collisional line shape effects in the rotovibrational ammonia spectrum (1991)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 719-733 
    Details
    ISSN: 0392-6737
    Keywords: Intensities and shapes of molecular spectral lines and bands ; PACS 33.20 ; Molecular spectra, grouped by wavelength ranges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary 455 self-broadening, self-shift and foreign gas (N2 and CO2) broadening measurements forv 2 andv 4 ammonia vibrational bands are compared to theoretical calculations performed in the frame of the semi-classical impact approximation. On the whole the agreement is satisfactory. However, a detailed analysis of the experimental and theoretical results shows some shortcomings in the accuracy of the experimental data and in the validity of the theoretical approach. General indications are given in order to improve further the description of the collisional line shape effects which is of great interest both for basic knowledge and for various applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02452217
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  • 10
    Electronic Resource
    Electronic Resource
    Self-consistent analysis of absorption and emission data forF A centres in alkali halides (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 127-139 
    Details
    ISSN: 0392-6737
    Keywords: Solid alkali halides ; Optical rotatory power ; Impurity and defect absorption in solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A theory which explains self-consistently the emission and the polarization rotation of transmitted light has been developed forF A centres in crystals with cubic symmetry. Azimuthal dependences ofF A luminescence in alkali halides are very informative for determining the electron-phonon interaction as well as the parameters related to the structural and optical quality for coulour centre lasers crystals. The theoretical results are applied to the interpretation of the luminescence properties ofF A (Li) centres in KCl, RbCl and KF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02451694
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