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101.
102.
We report observations of several wave-mixing and stimulated processes in pure potassium and mixed sodium-potassium vapors which are excited by a pulsed laser operating in the range 680–800 nm. When the laser is tuned to the potassium two-photon 4S6S transition, we observe stimulated emission on the various cascade transitions as well as four- and six-wave mixing. When the laser is tuned over the range 747 to 753 nm, which is well away from all atomic transitions, we observe strong forward and weak backward emission at the potassium 3D
3/24P
1/2 transition wavelength (1.17 m). However, this latter emission is only observed in the mixed sodium-potassium vapor. We present data on the excitation spectrum, forward to backward asymmetry, temporal dependence, and the laser power dependence of this emission. We speculate that twophoton photodissociation of the NaK molecule is responsible for this emission. 相似文献
103.
S. G. Masters K. M. Eriksen R. Fehrmann 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):227-233
Catalyst deactivation and hysteresis behavior in industrial SO2-oxidation catalysts have been studied in the temperature region 350–480°C by combined in situ EPR spectroscopy and catalytic activity measurements. The feed gas compositions simulated sulfuric acid synthesis gas and wet/dry deNOx'ed flue gas. The vanadium (IV) compound K4(VO)3(SO4)5 precipitated during all the investigated conditions hence causing catalyst deactivation. Hysteresis behavior of both the catalytic activity and the V(IV) content was observed during reheating. 相似文献
104.
The application of silylated controlled-pore glass (CPG) particles as a stationary phase for the liquid chromatographic separation of selected amino acids and amino hexoses is reported. Copper-loaded columns prepared from CPG particles whose surface was silylated to immobilize an ethylenediamine functional group were employed. Copper bleeding from the column occurred but was compensated by 10-4M copper in the ammoniacal eluent. Hydrolysis of the siloxane bonded to the surface limited the practical lifetime of a column to 50 h of continuous operation. 相似文献
105.
We prove exact controllability for Maxwell's system with variable coefficients in a bounded domain by a current flux in the
boundary. The proof relies on a duality argument which reduces the proof of exact controllability to the proof of continuous
observability for the homogeneous adjoint system. There is no geometric restriction imposed on the domain.
Accepted 25 June 2001. Online publication 19 October 2001. 相似文献
106.
Linda M Clutterbuck Leslie D Field Geoffrey B Humphries Anthony F Masters Mark A Williams 《应用有机金属化学》1990,4(5):507-512
The interaction of the olefin oligomerization catalyst system derived from [Ni(sacsac)(PBu3)Cl] (sacsac = pentane-2,4-dithionate = dithioacetylacetonate) with carbon monoxide (CO) has been examined by a combination of 31P NMR and FTIR spectroscopy. The catalyst is rapidly and completely inhibited by CO; however, removal of the CO restores catalytic activity. A CO-adduct of the active catalyst has a characteristic CO stretching frequency of 2042 cm?1, and δ31P 9.9 ppm. Carbon monoxide does not react with [Ni(sacsac)(PBu3)Cl], but [Ni(sacsac)(PBu3)(Cl)] reacts with any of Et2AlCl, BuLi, Li[Et3BH] or K[(s-Bu)3BH] under an atmosphere of carbon monoxide in the presence or absence of olefin to produce [Ni(PBu3)(CO)3], which has been identified by FTIR and 31P NMR. [Ni(sacsac)(PBu3)Cl] reacts completely with BuLi or K[(s-Bu)3BH] to form catalytically inactive species which yield active catalysts on addition of Et2AlCl. 相似文献
107.
Acetyl complexes of iron(II) and ruthenium(II) of the type (π-C5H5)(CO)LM(COCH3), where L = PPh3, P(OPh)3, P(cyclohexyl)3, PMe2Ph or CO for M = Fe, and PPh3 for M = Ru, are rapidly reduced to the corresponding ethyl complexes by BH3 · THF or B2H6/C6H6. In some cases hydrido complexes of the type (π-C5H5)(CO)LMH are also formed. The reaction has been studied by use of 1H NMR and the spectrum of (π-C5H5)(CO)(PPh3)FeC2H5, which shows several unusual features, is discussed in detail. It is suggested that the rate of reduction increases with increasing electron density at the metal centre.Acetyl complexes of other transition metals, i.e. Ir, Pt, Pd, Co and Mo, are also reduced to the corresponding ethyl compounds by B2H6/C6H6. 相似文献
108.
109.
110.
A kinetic equation for the motion of a particle of arbitrary size and mass through a moderately dense gas is derived and discussed. The “long-time tail” of the velocity correlation function is calculated and found to agree with existing results. For a Brownian particle, the theory gives the Stokes-Einstein law for the self-diffusion coefficient, with the shear viscosity given by its Enskog value. 相似文献