共查询到20条相似文献,搜索用时 15 毫秒
1.
D. Jumeau 《Journal of Physics and Chemistry of Solids》1979,40(9):669-674
X irradiation of NaNO2 single crystals, induces a motion of some NO2? ions, mainly around the axis perpendicular to their planes (a axis). The change in the orientation of NO2? is observed on the v2 vibration of NO2? (by IR absorption) and on the vibronic structures associated with the NO2? electronic transitions (by UV and visible absorption). Other centers, like no3?, are also produced by irradiation. Their evolution with temperature is studied. 相似文献
2.
L. A. Lisitsyna T. V. Grechkina V. I. Korepanov V. M. Lisitsyn 《Physics of the Solid State》2001,43(9):1680-1685
The spectral and kinetic parameters of electron-pulse-initiated transient absorption and emission of LiF crystals were studied using pulsed spectrometry with a nanosecond time resolution. The measurements were performed in the spectral region of 6 eV, the temperature range of 11–150 K, and within 10?8–10 s after the termination of an electron pulse. It is shown that the electron-pulse irradiation not only gives rise to F, V k , and H centers in the LiF crystal but also to certain short-lived defects of two types that differ in the spectral positions of the absorptive and radiative transitions, the lifetime, and the temperature dependence of the production efficiency. Defects of type I feature absorptive transitions at 5.5 and 5.1 eV and a radiative transition at 5.8 eV, whereas the absorptive transitions at 5.3 and 4.75 eV and a radiative transition at 4.4 eV are characteristic of type-II defects. It is found that a variation in the ratio between the concentrations of the different types of short-lived centers in the range of 11–150 K does not affect the quantum efficiency of the F centers. It is assumed that the observed centers are self-trapped excitons of various types. 相似文献
3.
Takeyuki Okada 《辐射效应与固体损伤》2013,168(1):337-342
Abstract Irradiation of KI near 150 K with KrCl excimer laser irradiation (hv=5. 58 eV) produces V centers causing V2 and V3 bands. The two bands exhibit 100-type dichroism. In KI containing V centers, the 111 cm?1 Raman signal attributed to I3- molecular ions is observed. Under KrCl excimer laser irradiation at low temperatures, resonance Raman scattering effects have been also studied for KI, NaI and LiI. 相似文献
4.
Ammonium alum crystals are colored electrolytically using a pointed cathode and a flat anode at low temperatures and under various voltages. SO3?, SO2? and O3? hole-trapped centers are produced in colored ammonium alum crystals. Characteristic absorption bands of SO3?, SO2? and O3? hole-trapped centers are observed in absorption spectra of colored ammonium alum crystals. Production and conversion of hole-trapped centers are explained. Current–time curves for electrolytic coloration of ammonium alum crystal and their relationship with electrolytic coloration process are given. 相似文献
5.
E. A. Radzhabov 《Optics and Spectroscopy》2016,120(2):294-299
The UV absorption spectra of F3? molecular ions in LaF3, SrF2, CaF2, and BaF2 crystals doped with rare-earth elements are studied. Comparison of radiation-colored and additively colored crystals reveals the absorption bands of F3? hole centers in the region near 6 eV. Nonempirical calculations of optical transitions agree well with experimental results. 相似文献
6.
Takeyuki Okada 《辐射效应与固体损伤》2013,168(1-4):271-275
Abstract The initial V2 and V3 bands observed after quenching of coloured KI crystals are found to be the superposition of absorption bands due to two kinds of V centres with ?110? and ?111? symmetries. The ratio of concentrations of the former to the latter V centers is estimated to be about 3:1. When a quenched crystal is irradiated at 19 K with V3-light in the 270-nm region, V centers are bleached forming I2-like centers. On the basis of the I3 molecule-ion model bound to a cation vacancy, a review is given of recent work on the photochemical conversion of V centers at low temperatures. 相似文献
7.
N. N. Loshkareva Yu. P. Sukhorukov B. A. Gizhevskii S. V. Naumov A. A. Samokhvalov A. S. Moskvin T. A. Belykh 《Physics of the Solid State》1998,40(3):383-388
Irradiation of various single-crystal CuO faces [ac,bc,(110)] with 4.6-MeV He+ ions has been found to result in reduction of CuO to Cu2O and Cu on the irradiated and unirradiated sides, lifting of forbiddenness from optical transitions in the [CuO4]7− electron center in the 0.7–0.95-eV energy range, a change in dichroism near the bands corresponding to transitions in the
hole centers, [CuO4]5−, and electron centers, [CuO4]7−, as well as in a resonant increase of absorption at 0.95–1.30 eV with an unusual polarization dependence. The results of
He+ irradiation of CuO single crystals are discussed in terms of a model of the nucleation of the phase of polar (electron and
hole) centers in copper-oxygen systems.
Fiz. Tverd. Tela (St. Petersburg) 40, 419–424 (March 1998) 相似文献
8.
Abstract The near UV absorption, steady-state polarized fluorescence excitation and time–-resolved fluorescence emission spectra of indole in argon matrix are reported. The absorption maxima of the four lowest singlet transitions were identified at 35095 cm?1(also the S1, 0 0–0 band), 37650 cm?1 (S2,0), 47415 cm?1 (S3,0), and 51680 cm?1 (S4,0). No distinct 0–0 band of the second transition was identified but the linearly polarized, steady-state fluorescence excitation spectrum indicates an onset of weak S2,0 bands on the blue side of the S1,0 0–0 peak (35095 + 400 cm?1). Only one fluorescence emission component, of 4.9±0.2 ns, was obtained by excitation over the S1, 0 0–0 + 565 cm?1 to S1,0 0–0 - 245 cm?1 domain. The reported data strongly suggest the 1Lb ?1A1 and 1La ?1A1assignment for the lowest and next lowest transitions, respectively. 相似文献
9.
Abstract Rutile, TiO2 having relatively high melting point exhibits strong optical absorption after neutron irradiation (8 × 1016 nr/cm2) at 15K. The band peak is located near 0. 96 μ having FWHM 0. 87 eV (at LNT). After inverse recovery at 120K, lattice defects due probably to F centers are annealed out at about 220K. 相似文献
10.
Electroluminescence from thin-film electroluminescent devices is found to be quenched after IR irradiation of the devices
in the interval between exciting voltage pulses. The IR irradiation decreases the emission intensity in the spectral range
530–540 nm, while increasing it between 640 and 690 nm. These effects are explained by IR-induced charge exchange between
the deep centers due to V
S
2+
and V
S
+
sulfur vacancies, an increase in the concentration of the latter vacancies, and the redistribution of the channels of impact
excitation of Mn2+ and V
S
+
centers in favor of V
S
+
centers. The cross section and rate of impact excitation of V
S
+
centers, the photoexcitation cross section for V
S
2+
centers, the IR radiation absorption coefficient, the internal quantum efficiency of electroluminescence, and the probability
of radiative relaxation of Mn2+ centers, as well as the electron multiplication factor in the phosphor layer, are evaluated. 相似文献
11.
V. V. Apollonov A. A. Pushkar’ T. V. Uvarova S. P. Chernov 《Physics of the Solid State》2008,50(9):1660-1663
The Dy3+ absorption and excitation spectra of BaY2F8 and BaYb2F8 single crystals are investigated in the ultraviolet, vacuum ultraviolet, and visible ranges at a temperature of 300 K. These crystals exhibit intense broad absorption bands due to the spin-allowed 4f-5d transitions in the range (56–78) × 10?3 cm?1 and less intense absorption bands that correspond to the spin-forbidden transitions in the range (50–56) × 10?3 cm?1. The Nd3+ absorption spectra of BaY2F8 single crystals are studied in the range (34–82) × 10?3 cm?1 at 300 K for different crystal orientations. 相似文献
12.
Abstract The origin of the blue color of calcites from Perewal (USSR) has been investigated. It is suggested that radiation-induced color centers (CO3 ?3, dislocation and twinning are involved in the coloring mechanism. Evidence is obtained from thermoluminescence and optical absorption of natural and X-irradiated calcite samples. 相似文献
13.
A. Bäcklin G. Hedin B. Fogelberg M. Saraceno R.C. Greenwood C.W. Reich H.R. Koch H.A. Baader H.D. Breitig O.W.B. Schult K. Schreckenbach T. Von Egidy W. Mampe 《Nuclear Physics A》1982,380(2):189-260
Levels up to 2.3 MeV in 156Gd have been studied using the (n, γ) reaction. Energies and intensities of low-energy γ-rays and electrons emitted after thermal neutron capture have been measured with a curved-crystal spectrometer, Ge(Li) detectors and a magnetic electron spectrometer. High-energy (primary) γ-rays and electrons have been measured with Ge(Li) detectors and a magnetic spectrometer. The high-energy γ-ray spectrum has also been measured in thermal neutron capture in 2 keV resonance neutron capture. The neutron separation energy in 156Gd was measured as Sn = 8535.8 ± 0.5 keV.About 600 transitions were observed of which ~50% could be placed in a level scheme containing more than 50 levels up to 2.3 MeV excitation energy. 42 of these levels were grouped into 15 excited bands. In addition to the β-band at 1050 keV we observe 0+ bands at 1168, 1715 and 1851 keV. Other positive-parity bands are: 1+ bands at 1966, 2027 and 2187 keV; 2+ bands at 1154 (γ-band) and 1828 keV; and 4+ bands at 1511 and 1861 keV. Negative-parity bands are observed at 1243 keV (1?), 1366 keV (0?), 1780 keV (2?) and 2045 keV (4?). Reduced E2 and E0 transition probabilities have been derived for many transitions. The ground band, the β- and γ-bands and the 0+ band at 1168 keV have been included in a phenomenological four-band mixing calculation, which reproduces well the experimental energies and E2 transition probabilities.The lowest three negative-parity (octupole) bands of which the 0? and the 1? bands are very strongly mixed, were included in a Coriolis-coupling analysis, which reproduces well the observed energies. The E1 transition probabilities to the ground band are also well reproduced, while those from the higher-lying 0+ bands to the octupole bands are not reproduced. Absolute and relative transition probabilities have been compared with predictions of the IBA model and the pairingplus-quadrupole model. Both models reproduce well the E2 transitions from the γ-band, while strong disagreements are found for the E2 transitions from the β-band. The IBA model predicts part of the decay features of the higher lying 2+2, 4+1 and 2?1 bands. 相似文献
14.
The centers are produced by different methods. Either the crystal, containingF centers in a high concentration, is annealed in an atmosphere of ammonia. Or the NH 4 + doped crystal is reduced withF centers. The optical absorption in the near infrared at 21 °K shows a well resolved doublett and another band at longer wavelengths. In the case of deuterated centers these bands are shifted by about √2 to longer wavelengths. These bands belong to the two stretching vibrations and the bending vibration of the NH 2 ? . In the UV a strong absorption band appears with satellites on its short wavelength side. Its maximum follows a Mollwo-Ivey relation. The satellites come from the simultaneous excitation of internal vibrations of the NH 2 ? . Their energy distance to the main maximum depends strongly on the hydrogen isotope. Excitation in the UV bands yields a flourescence in the visible region. It consists of two bands. They are interpreted as 0–0 transitions relative to the internal vibrations of the center. Their relative hight strongly depends on the temperature. We think that both bands are due to different positions of the amide ion in the excited state within the anion vacancy. From a detailed study of this temperature dependance typical activation energies can be derived. 相似文献
15.
Abstract Resonance Raman and electronic spectra of the μ-tris(bipyrazine)ruthenium(II)-hexaquis{ruthenium(II)EDTA} supramolecular complex are reported in this paper. Excitation in the 457–676 nm range leads to the selective enhancement of the Ru-bipyrazine vibrational peaks according to distinct patterns, supporting the assignment of the absorption bands at 670 and 490 nm as charge-transfer (MLCT) transitions from the [RuIIEDTA] dπ orbitals to the π1? and π2? LUMO levels of the bipyrazine ligand. A vibronic coupling mechanism involving the two excited states is suggested for the excitation at 490 nm. The occurrence of MLCT transitions in the [Ru(bpz)3]2+ central unity, around 440 nm, is supported by the Raman and fluorescence excitation profiles. 相似文献
16.
Sergei I. Bannov Valerian A. Nevostruev Boris A. Khisamov Mikhail B. Miklin 《辐射效应与固体损伤》2013,168(8):609-619
The structure and properties of the paramagnetic centers formed by γ-irradiation at 77 K in sodium sulfate doped with nitrate ions have been investigated by the EPR method. The NO2? 3, NO2 and SO? 4 radicals have been identified. The orientation of NO2? 3 relation to crystallographic axes is determined. In the 77-400 K temperature range the transformations of observable radicals have been studied. The mechanisms of their formation and thermal annealing have been discussed. The symmetry of nitrate ions in sodium sulfate was investigated by diffuse reflectance infrared Fourier transform spectroscopy. At the concentration of NO? 3 up to 5.5 × 1018 g?1 the nitrate ion was supposed to have a planar or pyramidal configuration of the D3h or C3V symmetries. At the concentration of the dopant higher than 5.5 × 1018 g?1 the nitrate ions with the C2V symmetry were observed. 相似文献
17.
Dipl.-Phys.Dr. W. Kleemann 《Zeitschrift für Physik A Hadrons and Nuclei》1970,234(4):362-378
Ag? centers in alkali halides give rise to a strong absorption band in the 300 nm region (formerly called “B band”). Its resolved triplet structure in CsCl suggests that it corresponds to the C band of the isoelectronic In+ center. Two very weak bands are found in several alkali halides in the 400 nm region. These new bands are assigned to the A and B transitions of the In+-type centers. This is supported by the doublet structure in the A band, and by the temperature dependence of the oscillator strength of the B band. In KCl∶Ag? the ratios of the oscillator strengths are found to bef c /f A =610 andf c /f B =3,400 at low temperatures. The energy parameters of Ag? centers are computed and compared with those of others 2-type centers. The electron-lattice coupling parameters are estimated from the Jahn-Teller splitting of the C band in CsCl and of the A band in KC1. The temperature dependence of the lifetime of the visible fluorescence suggests that a metastable state is involved in the emission process after a C band excitation. 相似文献
18.
ABSTRACT Thermally grown SiO2 thin films on a silicon substrate implanted with 100?keV silicon negative ions with fluences varying from 1?×?1015 to 2?×?1017 ions cm?2 have been investigated using Electron spin resonance, Fourier transforms infrared and Photoluminescence techniques. ESR studies revealed the presence of non-bridging oxygen hole centers, E′-centers and Pb-centers at g-values 2.0087, 2.0052 and 2.0010, respectively. These vacancy defects were found to increase with respect to ion fluence. FTIR spectra showed rocking vibration mode, stretching mode, bending vibration mode, and asymmetrical stretching absorption bands at 460, 614, 800 and 1080?cm?1, respectively. The concentrations of Si–O and Si–Si bonds estimated from the absorption spectra were found to vary between 11.95?×?1021 cm?3 and 5.20?×?1021 cm?3 and between 5.90?×?1021 cm?3 and 3.90?×?1021 cm?3, respectively with an increase in the ion fluence. PL studies revealed the presence of vacancies related to non-bridging oxygen hole centers, which caused the light emission at a wavelength of 720?nm. 相似文献
19.
20.
V. N. Verma 《光谱学快报》2013,46(10):591-601
Abstract The electronic absorption spectrum of mesitylene vapour has been photographed on a Q-24 Medium Quartz Spectrograph. The molecule belongs to D3h symmetry and the transition is A→1A2 which is forbidden and due to that the (0,0) band does not appear in the spectrum. The position of (0,0) band in this case has been fixed at 36562 cm?1 with the help of 0→1 and 1→0 transitions. There are 66 bands and most of them are assigned in terms of two ground state frequencies of magnitudes 278 and 519 cm?1 and 7 excited state frequencies of magnitudes 267, 436, 554, 968, 1268, 1386 and 1575 cm?1 相似文献