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1.
The optical properties of deep hole traps H4 and H5 in p type and of the deep electron trap E11 in n type InP, introduced by electron irradiation, have been studied using deep level optical spectroscopy. Comparison of the optical threshold with the thermal activation energy of H5 level shows that it is highly relaxed with a Frank-Condon shift dFc = 0.45 eV. The electron level E11 is weakly relaxed and its optical cross section σ 0 is well accounted for by transitions to the Γ6c minimum. The optical absorption σp0 associated to level H4 shows two successive onsets at = 0.5 and = 1.2 eV which can be attributed to hole transitions to the Γ7–8 and to the L4–5 valence band extrema, respectively. The deduced Frank-Condon shift, dFc = 0.23 eV, agrees with the measured difference of 40 meV between its apparent activation energy Ea and its thermal activation energy ET.  相似文献   

2.
The synchrotron radiation spectrum is calculated for relativistic electrons in the case where no restriction is placed on the strength of the magnetic field. It is shown that in intense fields H? H0 = m2c3/e0? =4.41 · 1013 G a major contribution to the total radiation intensity comes from transitions to the ground state and also to weakly excited levels. In particular, the contribution from transitions to the ground state (final electron energy E' =mc2) for electrons of initial energy E = 10 MeV in a field H = 2H0 is 14% of the contribution from transitions to highly excited states (E'?mc2).  相似文献   

3.
An exact solution to the Schrödinger equation for the ground state of two-dimensional Pauli electrons in a nonuniform transverse magnetic field H is presented for two cases. In the first case, the field H depends on a single variable, H = H(y), while in the second case, the field is axially symmetric, H = H(ρ), ρ2=x 2+y 2. The electron density distributions n = n(y) and n = n(ρ) that correspond to a completely filled lower level are found. For quasiuniform fields of fixed sign, the functions n(y) and n(ρ) are locally related to the magnetic field: n(y) = H(y)/?0 and n(ρ) = H(ρ)/?0, where ?0 = hc/|e| is a magnetic flux quantum. Magnetic fields are considered that are periodic, singular, and bounded in the plane xy. Finite electron objects in a nonuniform magnetic field are analyzed.  相似文献   

4.
Electronic spectra of a series of weakly bound clusters consisting of argon (Arn, n=1-4) bound to the butadiyne cation, C4H2+, have been recorded in the visible range from 440 to 520 nm by photodissociation. The C4H2+ fragment signal was recorded as a function of the laser wavelength during excitation of the AX electronic transition. The observed transitions were assigned to the band origin of the cationic complexes and to vibronic bands involving excitation of the ν3 and ν7 vibrational modes of the C4H2+ moiety, as well as combination bands of these modes. Comparison of the photodissociation spectra of the various clusters reveals a small blue shift, 25 cm−1 of the band maxima relative to the corresponding transitions reported from gas phase spectra of the bare C4H2+ cation. The magnitude of the blue shift of each band increases with successive Ar solvation up to n=3. Furthermore, each band becomes increasingly broadened towards the red with the addition of Ar atoms due to an increasing number of unresolved transitions involving excited intermolecular modes.  相似文献   

5.
A pair of 1.5 μm semiconductor laser frequency standards have been developed for optical telecommunications use, stabilised to transitions of 12C2H2 and 13C2H2, using cavity-enhanced Doppler-free saturation absorption spectroscopy. The absolute frequencies of 41 lines of the ν1 + ν3 band of 12C2H2, covering the spectral region 1520-1545 nm, have been measured by use of a passive optical frequency comb generator, referenced to 13C2H2 transitions of known frequency. The mean experimental uncertainties (coverage factor k = 1) of the frequency values are 3.0 kHz (type A) and 10 kHz (type B). Improved values of the band origin ν0, rotational constants B′ and B″, and centrifugal distortion coefficients D′, D″, H′, and H″ are presented.  相似文献   

6.
The high resolution absorption spectrum of the H218O isotopologue of water has been recorded by Intracavity Laser Absorption Spectroscopy (ICLAS) with a sensitivity on the order of αmin ∼ 10−9 cm−1. The 11 520-12 810 cm−1 spectral region corresponding to the 3ν + δ decade of vibrational states, was explored with an ICLAS spectrometer based on a Ti:Sapphire laser. It allowed detecting transitions with an intensity down to 10−27 cm/molecule which is about 100 times lower than the weaker line intensities available in the literature, in particular in the HITRAN database.The rovibrational assignment was performed on the basis of the results of variational calculations and allowed for assigning 3659 lines to the H216O, H218O, H217O, HD16O and HD18O species, leaving only 1.7% unassigned transitions. A line list including 1712 transitions of H218O has been generated and assigned leading to the determination of 692 rovibrational energy levels belonging to a total of 16 vibrational states, 386 being newly observed. A deviation on the order of 25% has been evidenced for the average intensity values given by HITRAN and the results of variational calculations. Ninety two transitions of the HD18O isotopologue could also be assigned and the corresponding upper rovibrational levels are given.  相似文献   

7.
The H2 opacity arising from the pure-rotational hexadecapole-induced U0(J) transitions occurring during H2H2 and H2He collisions, and from the hexadecapole-induced U0(J) + S0(J′) and the quadrupole-induced S0(J) + S0(J′) transitions in H2He collisions, has been calculated. The U0(J) and S0(J) + S0(J′) contributions from H2H2 collisions are important H2 opacities in the frequency range from 700–3000 cm?1 for temperatures appropriate to the outer planets. It is concluded that this opacity is needed in addition to the opacity from the extrapolation of the 0-0 and 1-0 H2H2 collisionally induced bands to interpret the spectrum at 5 μm for the outer planets.  相似文献   

8.
Line emission spectrum of a laser plasma produced in an argon cluster jet target was measured on the n 1 P1?11 S 0 (n=5–9) transitions of the helium-like Ar XVII ion for a pulse duration varying from 45 fs to 1.1 ps and a constant fluence of ~105 J/cm2. The independent modeling of the relative intensities of the transitions from the n=5,..., 10 levels, as well as of the 21 P 1? 12 S 0 and 23 P 1?12 S 0 lines and dielectronic satellites indicates that the electron temperature is anomalously low and that the electron density in emitting plasma increases with shortening the laser pulse. The excitation from the ground state by a small fraction of hot electrons is expected to be the main channel of populating the Ar XVII levels.  相似文献   

9.
The heat capacity of the layer compounds tetrachlorobis (n-propylammonium) manganese II and tetrachlorobis (n-propylammonium) cadmium II, (CH3CH2CH2NH3)2MnCl4 and (CH3CH2CH2NH3)2CdCl4 respectively, has been measured over the temperature range 10 K ?T ? 300 K.Two known structural phase transitions were observed for the Mn compound in this temperature region: at T = 112.8 ± 0.1 K (ΔHt= 586 ± 2 J mol?1; ΔSt = 5.47 ± 0.02 J K?1mol?1) and at T =164.3 ± (ΔHt = 496 ± 7 J mol?1; ΔSt =3.29 ± 0.05 J K?1mol?1). The lower transition is known to be from a monoclinic structure to a tetragonal structure, while the upper is from the tetragonal phase to an orthorhombic one. From comparison with the results for the corresponding methyl Mn compound it is deduced that the lower transition primarily involves changes in H-bonding while the upper transition involves motion in the propyl chain.A new structural phase transition was observed in the Cd compound at T= 105.5 ± 0.1 K (ΔHt= 1472.3 ± 0.1 J mol?1; ΔSt = 13.956 ± 0.001 J K?1mol?1), in addition to two transitions that have been observed previously by other techniques. The higher of these transitions(T = 178.7 ± 0.3 K; ΔHt = 982 ± 4 J mol?1 ΔSt = 6.16 ± 0.02 J K? mol?1) is known to be between two orthorhombic structures, while the structural changes at the lower transition (T= 156.8 ± 0.2 K; ΔHt = 598 ± 5 J mol?1, ΔSt = 3.85 ± 0.03 J K?1 mol?1) and at the new transition are not known. It is proposed that these two transitions correspond respectively to the tetragonal to orthorhombic and monoclinic to tetragonal transitions in the propyl Mn compounds.In addition to the structural phase transitions (CH3CH2CH2NH3)2MnCl4 magnetically orders at t? 130 K. The magnetic contribution to the heat capacity is deduced from the heat capacity of the corresponding diamagnetic Cd compound and is of the form expected for a quasi 2-dimensional Heisenberg antiferromagnet.  相似文献   

10.
The pure rotational spectra of three silicon isotopologues of HSiI and two isotopologues of DSiI have been recorded by pulsed-jet Fourier transform microwave (FTMW) spectroscopy. Neon was passed over dry ice cooled H3SiI or D3SiI and introduced into the pulsed valve of the FTMW spectrometer. The monoiodosilylenes HSiI and DSiI were produced in situ with a 1000 V DC-discharge nozzle. Only a-type transitions occur in monoiodosilylene from 6 to 26 GHz. We observe Ka = 0 a-type transitions for H28SiI, H29SiI, H30SiI, and D29SiI, and both Ka = 0 and 1 a-type transitions for D28SiI. Rotational constants, centrifugal distortion constants, iodine nuclear quadrupole coupling constants, and nuclear spin–molecular rotation constants were measured.  相似文献   

11.
The Ca2.95−yDy0.05B2O6:yNa+ (0≤y≤0.20) phosphors were synthesized at 1100 °C in air by the solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE), photoluminescence (PL) spectra and thermoluminescence (TL) spectra. The PLE spectra show the excitation peaks from 300 to 400 nm due to the 4f-4f transitions of Dy3+. This mercury-free excitation is useful for solid-state lighting and light-emitting diodes (LEDs). The emission of Dy3+ ions on 350 nm excitation was observed at 480 nm (blue) due to the 4F9/26H15/2 transitions, 575 nm (yellow) due to 4F9/26H13/2 transitions and 660 nm (red) due to weak 4F9/26H11/2 emissions. The PL results from the investigated Ca2.95−yDy0.05B2O6:yNa+ phosphors show that Dy3+ emissions increase with the increase of the Na+ codoping ions. The integral intensity of yellow to blue (Y/B) can be tuned by controlling Na+ content. By the simulation of white light, the optimal CIE value (0.328, 0.334) can be achieved when the content of Na+-codoping ions is y=0.2. The results imply that the Ca2.95−yDy0.05B2O6:yNa+ phosphors could be potentially used as white LEDs.  相似文献   

12.
A diode laser spectrometer that was operated in sweep integration mode was used to measure individual line strengths for 17 R-branch transitions of the (ν4 + ν5)0 combination band of 12C2H2 at 7.4 μm. Analysis of these results gives a band strength Sv = 64.4 ± 2.0 cm?2 atm?1 at 296 K. Line-broadening parameters for several of these transitions were determined by using both N2 and He as broadening gases.  相似文献   

13.
It is shown from a general point of view that the coexistence of ferro- and antiferromagnetism with a symmetry-breaking is possible in certain itinerant electron systems where the wave vector dependent susceptibility χq0 without the electron-electron interaction has two peaks at q = 0 and q = Q, the antiferromagnetic vector. The conditions for the coexistence and the possible phase diagrams in the H-T plane and the nature of phase transitions are discussed.  相似文献   

14.
Experiments with the tetragonal antiferromagnet Nd2CuO4 in the temperature range 1.5 K < T < T N = 245 K show that the magnetic moments of Cu2+ possess an exchange-noncollinear magnetic structure of the “square” type, which has the form of an exchange doublet whose components exhibit different chiralities (Γ4 and Γ5 phases). Between these phases, consecutive phase transitions Γ4 ? Γ5 ? Γ4 with a change in chirality take place at temperatures T1 = 30 K and T2 = 70 K. The electron and nuclear magnetic resonances (natural frequencies and susceptibilities) associated with excitation of magnons (due to the magnetoelectric and antiferroelectric interactions) by an ac electric field E(t), as well as a variable magnetic field H(t) applied in the case of a constant electric field E0, are calculated. It is predicted that nuclear magnetic resonance is excited by an ac electric field at frequencies determined by hyperfine fields of the sublattices. The change in the resonance frequencies upon the above chiral phase transitions are analyzed (being first-order phase transitions, these transitions possess a number of features associated with the chirality of the magnetic structures).  相似文献   

15.
A new Penning-electron-Penning-ion coincidence method is described. It is applied to the study of the thermal reaction of He(23S) with H2. The main results reported are separate electron energy spectra that are coincident with the three different ions formed: HeH2+, HeH+ and H2+. Based on these results it is shown that the Penning reaction of the He(23S)/H 2 system proceeds in two well-separated steps: (i) ionization at distances R (HeH2) ? 6a0 in which H2+ (v) is formed in different vibrational states; and (ii) reactive collision of H2+ (v) with He. For the second step the variation of the branching ratios with vibrational quantum numbers v = 0 to v = 10 is derived, and it is shown that these branching ratios may be regarded as relative vibrational-energy-dependent cross-sections for the collision of H2+ (v) with He at an average relative kinetic energy of ~20 meV.  相似文献   

16.
X-band electron paramagnetic resonance (EPR) studies on divalent copper ions embedded in KMgClSO4·3H2O single crystals have been performed at low temperature (123 K). The angular variation of the EPR spectra reveals the presence of two Cu2+ sites, which have different orientations. The spin-Hamiltonian parameters of this six-coordinated cupric ion have been evaluated from the EPR spectra at 123 K. The forbidden lines due to ΔmI=±1 transitions are observed in between allowed transitions. The temperature variation EPR studies have also been performed both for a single crystal and a polycrystalline sample. The ground state wavefunction of Cu2+ ions has been estimated and is found to be an admixture of d3z2r2 and dx2y2. The temperature variation of the EPR spectra reveals that Cu2+ ions exhibit dynamic Jahn-Teller effect. From the polycrystalline EPR data, the temperature dependent magnetic susceptibilities are evaluated and discussed.  相似文献   

17.
High-sensitivity Intracavity Laser Absorption Spectroscopy (ICLAS) is used to measure the high resolution absorption spectrum of H218O between 12,580 and 13,550 cm−1. This spectral region covers the 3v+δ polyad of very weak absorption. Four isotopologues of water (H218O, H216O, H217O, HD18O) are found to contribute to the observed spectrum. Spectrum analysis is performed with the aid of variational calculations and allowed for assigning 1126 lines belonging to H218O, while only 160 H218O lines are included in the HITRAN-2008 database. Altogether, 823 accurate energy levels of H218O are determined from transitions attributed to 26 upper vibrational states, 438 of them being reported for the first time. New information includes energy levels of four newly observed vibrational states of H218O: (2 4 0), (1 4 1), (0 4 2) and (2 3 1) at 13,167.718, 13,212.678, 13,403.71 and 15,073.975 cm−1, respectively. H218O transitions involving highly excited bending states like (1 6 0), (0 6 1), (0 7 1), (1 7 0), (0 9 0) and even (0 10 0) have been identified as a result of an intensity borrowing from stronger bands via high-order resonance interactions. Thirty-six new energy levels of H217O, present with a 2% relative concentration in our sample, could be determined. The rotational structure of the (0 2 3) state of HD18O at 13,245.497 cm−1 is also reported for the first time.  相似文献   

18.
The electronic absorption spectra of [(CH3)3NH] MnCl3.2H2O single crystals are reported in the 15,000–45,000 cm-1 region. In addition to the normally studied sextet → quartet transitions, special attention has been paid to the sextet → doublet transitions. Crystal field parameters evaluated (including the Trees' correction factor) to fit the observed spectra are B = 800, C = 2900, Dq = 680, and α = 76 cm-1.  相似文献   

19.
We found new bands in the absorption spectra of Pt(II) and Pd(II) complexes of octaethylporphyrin and tetraphenylporphyrin that differ in the nature, number, and position of their side substituents. The bands are observed at 295 K in the range 570–690 nm and are attributed to spin-forbidden transitions from the ground S 0 state to the excited T 1 and T 2 triplet states (the internal heavy atom effect). We determined the frequency distribution, number, and nature of these transitions, as well as their extinction coefficients (? = 6.0–210.0 M?1 cm?1), using computer decomposition of complex contours into Gaussian components and additional data obtained from the phosphorescence and phosphorescence excitation spectra of these complexes (295–77 K). In comparison to Pd complexes of porphyrins with planar macrocycles, nonplanar distortions of the tetrapyrrole macrocycle in the ground S 0 state of the sterically hindered PdOETPP molecule cause a bathochromic shift of the bands of the electronic spin-forbidden S 0T 1 and S 0T 2 transitions, as well as an increase in their extinction coefficients. For the PdOEP-Ph(o-NO2) molecule, which contains the electron acceptor nitro group, an absorption band attributed to an electronic transition from the ground state S 0 to a charge transfer state (λmax = 905 nm, ? = 10.0 M?1 cm?1) is observed at 295 K.  相似文献   

20.
We measured room-temperature H2O spectra of the 3ν polyad within the wave number range 10 603 cm−1 to 10 852 cm−1 using frequency-stabilized cavity ring-down spectroscopy. More than 70 transitions, divisible into two groups based on their relative intensities (strong and weak) were investigated. For the 23 lines comprising the set of strong transitions, the water vapor sample was prepared as a dilute mixture in a steady flow of N2 carrier gas, and the measurement of the water vapor sample number density was linked to primary methods of humidity generation. For these strong transitions, the measured line intensities were within 1% of previous measurements. The line intensity measurements of the weaker H2O transitions, were made on samples of static pure water vapor, and these results were systematically greater than previous measurements by approximately 20%.  相似文献   

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