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1.
The adsorption of indium on clean (111) silicon surfaces is studied by flash desorption. Two adsorption phases are found: a constant-energy phase which saturates at and a second phase which increases with the adatom population n. The temperature of the desorption peak of this phase decreases when n increases. The adsorption energy of In on (111) Si is calculated by the Gyftopoulos theory, and the calculated and experimental results are compared. A very small charge transfer between the adatoms and the surface, equal to or smaller than 0.02 electron per adatom, is found. 相似文献
2.
The decomposition of D2CO, CH3OD and HCOOH on Pt(110) and of D2CO on Pt(S)-[9(111) × (100)] was studied by molecular beam relaxation spectroscopy. D2CO and CH3OD evolved CO and H2 via a desorption limited sequence of elementary steps. The rate constant for CO desorption from Pt(110) was 6 × 1014exp(? 35.5 · RT) s?1, and from Pt(S)-[9(111) × (100)] it was 1 × 1015 exp(?36.2 ) s?1. On Pt(110) the rate constant for hydrogen formation was 100 ± 1exp(?24 ) · s. On Pt(S)-[9(111) × (100)] two pathways for H2 formation existed with rate constants of 8.7 × 10?2exp( ?24.9 ) · s and 3.2 × 10?3 exp(?19.5 ) s. These pre-exponential factors are in order of magnitude agreement with values typical of hydrogen recombination on other metals. When a small amount of sulfur ( ~ 0.1 ML) was adsorbed on the stepped Pt surface, only one pathway for H2 formation existed due to blockage of stepped sites. A similar result was obtained when a beam of CO was impinged on the surface. Formic acid decomposed via a branched process to form primarily CO2 and H2. 相似文献
3.
M. Villedieu N. Devismes A.M. de Goër 《Journal of Physics and Chemistry of Solids》1977,38(9):1063-1070
The effect of γ irradiation at 300 K on the concentrations of vanadium ions V3+, V4+ and V2+ in Al2O3 has been studied quantitatively, using three techniques: optical absorption (V3+), low temperature thermal conductivity measurements (V4+) and EPR (V2+). Several single crystals of Al2O3 doped with vanadium in a large range of concentration have been measured. The evolution of the respective concentrations by γ irradiation as a function of the total vanadium content C is quite different in the two regions and C larger than this value. A consistent analysis of the results has nevertheless been achieved, leading to the determination of the absolute concentrations of the three ions in the as-received and γ irradiated states for all samples with (room temperature annealing is observed above this value). The concentrations of V4+ and V2+ ions are always small, but V4+ ions are more stable: they are present in the as-received state at a level of 1% of the total concentration and a maximum value of is observed in the γ irradiated state; on the other hand there are less than 4.7 × 1015V2+ ions per cm3 in the as-received state and the maximum value is only . Charge transfer between V ions only is not sufficient to explain the experimental results and other defects must be involved in the γ irradiation effect. 相似文献
4.
J.F. Seely R.H. Dixon R.C. Elton J.G. Lunney 《Journal of Quantitative Spectroscopy & Radiative Transfer》1982,27(3):297-306
The Lyman-α and adjacent dielectronic satellite lines have been observed in the spectra from laser-irradiated solid targets. In a carbon plasma from a planar target, the relative intensity of the satellite line of C(V) increases as a function of electron density in the range 8 × 1019 to 2 × 1020 cm?3. As analysis of a series of imploded microballoon experiments indicates that the and satellite radiation of Si(XIII) increases for electron densities 1 × 1022?2 × 1023 cm?3. The satellite intensity distributions have been numerically simulated using a rate equation model. It is shown that the carbon and silicon satellite data may be interpreted in a consistent manner, and the extension to higher atomic numbers Z and higher electron densities is considered. 相似文献
5.
EPR of 61Ni+ doped CuGaS2 at 4.2 K leads to the following experimental data: . High axial field splitting of 2T2 state stabilizes the center against Jahn-Teller interaction. Covalency reduction factor k is 0.76. 相似文献
6.
The isothermal compressibilities of pristine graphite and stages 1 and 2 potassium-graphite have been measured at room temperature. Diamond anvil X-ray diffraction techniques were employed to determine the c-axis lattice constant as a function of hydrostatic pressure up to 12 kbar. The compressibilities were found to be (2.73±0.09)×10-12, (2.13±0.09)×10-12, (5.3±0.8)×10-12 and for graphite, KC8, stage 2 KC24 and stage 3 KC24, respectively. The compressibility of KC8 was comparable to that of RbC8 deduced from neutron scattering experiments. 相似文献
7.
The cyclotron resonance of inversion-layer electrons on (100)p-type Si is found to depend sensitively on an externally applied compressive stress. At low temperatures (T ? 10 K) we observe a considerable increase of the cyclotron mass m1c with stress S along the [001] direction. The effect is most strongly observed at low electron densities ns. For and ns~2 × 1011cm-2 we obtain instead of the expected 0.2m0. Along with this change of a strong narrowing of the resonance is noted. Raising the temperature gives an additional ns- dependent increase of . 相似文献
8.
J.C.D. Brand U.D. Deshpande A.R. Hoy S.M. Jaywant 《Journal of Molecular Spectroscopy》1983,100(1):143-150
The E-B (0g+-0u+) band system of Br2 has been investigated at Doppler-limited resolution using polarization labeling spectroscopy. Merged E state data for the three naturally occurring isotopes in the range vE = 0–16, expressed in terms of the constants for 79Br2, are (in cm?1) Y0,0 = 49 777.962(54), Y1,0 = 150.834(22), Y2,0 = ?0.4182(28), Y3,0 = 6.6(11) × 10?4, Y0,1 = 4.1876(28) × 10?2, Y1,1 = ?1.607(16) × 10?4, and Y0,2 = 1.39(39) × 10?8. The bond distance is , and the diabatic dissociation energy to . 相似文献
9.
Measurements have been made of the transit times of pulses of longitudinal and transverse ultrasonic waves propagating in single crystal LaB6 at room temperature. A unique set of values for the three independent elastic constants has been calculated from the resultant velocities and is; C11 = (45.33 ± 0.11) × 1011dynecm-2, and C44 = (9.01 ± 0.05) × 1011dyne/cm2. The Debye temperature of LaB6 from these measurements is 773 K, which agrees relatively well with the X-ray Debye temperature, however, differs much from the calorimetric and electrical resistance Debye temperatures. 相似文献
10.
H. Venghaus 《Journal of luminescence》1978,16(3):331-341
Luminescence measurements were performed on high purity epitaxial n-GaAs for various excitation intensities I0 in the range . The luminescence line corresponding to the radiative decay of the shallow donor bound exciton, (D0, X), broadens with increasing I0 and appears as a doublet for , while the two-electron replica of the (D0, X) remains a single narrow line. The doublet structure of the (D0, X) at elevated excitation levels is due to missing luminescence intensity in the center of the line as a consequence of low (D0, X) concentration in a layer extending 1–2 μm from the sample surface into the bulk. The low concentration of (D0, X) is attributed to capture of (D0, X) quanta into surface states, extending to lower energies from the Fermi level fixed by the shallow donors. Comparison of the present results with luminescence spectra obtained by various authors reveals, that unexplained spectral features in the (D0, X) region of n-GaAs reported in the literature are a consequence of high excitation intensity and correspond to the effect reported here. In partly compensated p-GaAs with donor concentrations as given above, the (D0, X) did not transform into a doublet structure even at excitation intensity. 相似文献
11.
Peter J Domaille Timothy C Steimle David O Harris 《Journal of Molecular Spectroscopy》1977,68(1):146-155
The pure rotational spectrum of the state of the gaseous SrF radical has been measured using microwave optical double resonance (MODR) techniques. The analysis fully confirms the recent dye laser excitation spectrum and rotational assignment of the system. Transitions were measured in both the v″ = 0 and v″ = 1 states to give values of Be″ = 0.250533 cm?1, αe″ = 1.546 × 10?3 cm?1 and γ″ (spin-rotation) = 2.49 × 10?3 cm?1. General qualitative features of MODR in 2Σ+ states are treated and suggested improvements for obtaining experimental hyperfine constants are discussed. The more precise ground state constants are merged with the B-X optical analysis to obtain a more accurate set of constants for both states. 相似文献
12.
A. Baldacci S. Ghersetti S.C. Hurlock K. Narahari Rao 《Journal of Molecular Spectroscopy》1976,59(1):116-125
The rotational structure of about 40 bands of 12C2HD observed in the region 6000?600 cm?1 has been measured and interpreted with the purpose of determining a comprehensive set of molecular constants for this isotopic variety of acetylene. Combining these data with the results for 12C2H2 and 12C2D2, a reevaluation of the equilibrium internuclear distances for the acetylene molecule has been made: and were obtained. This paper presents all the molecular constants derived in this study. 相似文献
13.
Experimental data concerning the electrical conduction and Hall coefficient in HgTe samples with acceptor states have been collected and analysed. In the analysis three ranges of acceptor concentration have been distinguished: a low concentration range up to about 5 × 1015 cm?3 (pure samples), a high concentration range from 1016 to 1018 cm?3 (p-like samples), and an extremely high concentration range above 1018 cm?3 (p-type samples). In pure HgTe samples the holes are in the valence band, in p-like samples the “holes” are in the impurity band, and in p-type HgTe samples the holes are in a strong mixing impurity-valence band. The mobility of holes in the valence band is of the order of . The mobility of “holes” in the impurity band decreases with increasing impurity concentration from about to . The mobility of holes in p-type HgTe samples is independent of the acceptor concentration and is equal to . 相似文献
14.
R.B. Hallock 《Physics letters. A》1973,43(5):445-446
The static structure factor of helium gas has been measured at densities of 3.45 × 10?3, 2.66 × 10?3 and at a temperature of 4.995 K. The results are in qualitative agreement with the limited theoretical work available. 相似文献
15.
D. Mazumdar P.A. Govindacharyulu D.N. Bose 《Journal of Physics and Chemistry of Solids》1982,43(9):933-940
A Study of electronic conductivity using the d.c. polarization technique has been carried out in α and β-AgI which shows the former is a hole and the latter an electron conductor. Activation energies of undoped and Cu-doped single crystals and polycrystalline β-AgI were found to be 0.46 eV, 0.34 eV and 0.44 eV respectively and can be related to electron trap depths. The electron transference number () for polycrystalline β-AgI was found to be 0.008 at 306 K. The activation energy for hole conduction in α-AgI was determined to be 0.97 eV in agreement with previous XPS studies.Transient measurements have also been conducted using the charge transfer technique in double cells of polycrystalline β-AgI. The carrier concentration Cθ and electron mobility μθ, have thus been estimated to be 1.8 × and 5.14 × 10?5?sec. respectively at 306 K, while the double layer capacitance was 0.496 . 相似文献
16.
Elías López-Cruz 《Solid State Communications》1980,35(12):921-924
The I–V characteristics of the UV-induced double injection of carriers into sulfur single crystals are reported. These characteristics display a quadratic behavior as a function of the electric field up to E≈7×103 where it changes to a cubic law dependence. The V2 branch can be accounted for by means of the one carrier space charge limited current. The cube law dependence arises as a result of the recombination limited two-carrier injection according to the model of Lampert and Mark. We estimate values for the common lifetime τ = 4.8×10?3 sec, and the trap modulated mobility of holes . 相似文献
17.
When Langmuir-Blodgett films, consisting of a mixture of a long chain carboxylic acid and its salt are immersed in benzene, the acid dissolves, while the salt remains as a skeleton. The density of the film is lowered in this way and so is the refractive index. The process can thus be followed by performing ellipsometric measurements as a function of time of skeletonization. It is established that skeletonization is, in first instance, a diffusion-controlled process with a diffusion coefficient of about at room temperature. The salt also slowly dissolves at a rate of about . 相似文献
18.
The Raman active fundamentals ν1(A1g), ν2(Eg), ν5(F2g), and the overtone 2ν6 of SF6 have been investigated with a higher resolution and the band origins were estimated to be: ν1 = 774.53 cm?1, ν2 = 643.35 cm?1, ν5 = 523.5 cm?1, and 2ν6 = 693.8 cm?1. Raman and infrared data have been combined for estimation of several anharmonicity constants. The ν6 fundamental frequency is calculated as 347.0 cm?1. From the analysis of the ν2 Raman band, the following rotational constants of both the ground and upper states have been calculated: ; . 相似文献
19.
G. Tarrago M. Dang-Nhu G. Poussigue G. Guelachvili C. Amiot 《Journal of Molecular Spectroscopy》1975,57(2):246-263
High resolution spectra of the ν3 band of methane, 12CH4, were recorded by using a “third generation vacuum Fourier interferometer”; a large pressure range (from 0.009 to 10 Torr) with a sample path fixed at eight meters was used, enabling observation of transitions with intensity ratios as low as . More than 350 forbidden transitions of the ν3 band, including about 125 transitions of the Q+ branch, were unambiguously identified. Of the 277 transitions retained for computations, one-hundred have 11 ≤ J ≤ 16. From combination difference relations using pairs of transitions having the same upper state energy level (forbidden-allowed and forbidden-forbidden pairs were used), 276 independent differences between ground state energy levels could be determined with uncertainties of about 0.001 cm?1.These data yielded the following values for the ground state structure constants of 12CH4 along with their standard deviations (in cm?1): , , , , , , Thus, for the first time, the scalar constant π0 has been evaluated and ir values have been obtained for the two tetrahedral constants ?0 and ξ0; furthermore, these values are in very good agreement with the ones recently determined from radiofrequency data, i.e., in cm?1: , , From these values, the 276 differences can be reproduced with an overall rms deviation equal to 0.0009 cm?1.Finally, the ground state energies of 12CH4 have been calculated for J ≤ 16. 相似文献
20.
Capacitance measurements on N-type As, P, and Sb-doped Si samples have been made between 4.2 and 1.35°K, from 0.3 to 100 kHz as a function of (ND ? NA) [high purity to 2.7 × 1018/cm3]. From the dielectric constant variation with (ND ? NA) donor polarizabilities αAS, αP, and αSb are found respectively to be . 相似文献