Annealing effect on InAs islands on GaAs(0 0 1) substrates studied by scanning tunneling microscopy

Post-annealing effects on InAs islands grown on GaAs(0 0 1) surfaces have been investigated by scanning tunneling microscopy (STM) connected to molecular beam epitaxy (MBE). It is found that for islands grown by 1.6 ML InAs deposition at 450 °C, post-annealing at 450 °C in an As₄ atmosphere causes dissolving of the InAs islands. In contrast, for larger islands obtained by 2.0 ML InAs deposition at 450 °C, the post-annealing leads to coarsening of the islands. The result can be explained in terms of a critical nucleus in heterogeneous nucleation.     

Ultra-High Quality Cavity with 1.5 ppm Loss at 1064 nm

Characterization of an ultra-low loss and high finesse Fabry-Perot cavity at 1064 nm is reported. The characteristics are obtained from measurements of cavity decay time, frequency response and transmission efficiency. The results show that the mirrors have the loss of 1.5 ppm including absorption and scattering losses and the reflectance of 99.9873% which corresponds to a cavity finesse of 2.48X10⁴.     

Synthesis of (Aza)n[3n]cyclophanes as host molecules

(Aza)_n[3ⁿ]cyclophanes were synthesized by the coupling reaction of p-toluenesulfonamide and bis(halomethyl) derivatives in the presence of a base (K₂CO₃, NaH etc.) using DMF, dioxane etc. as a solvent, in acceptable yields. Tetraaza macrocyclic compound (the dimer in Fig. 1) obtained by the coupling of 2,11-diaza[3.3]metacyclophane with 1,3-bis(bromomethyl)benzene gavea 1:1 adduct with benzene.Presented partly at the 42nd Autumn Annual Meeting of the Chemical Society of Japan, Sendai, September, 1980; Abstr. No. 1J17.     

The kinetic study of thermal dehydration stages of SrCl2 · 2H2O and its deuterium analog

The kinetic deuterium isotope effect in the thermal dehydration stages of powdered SrCl₂ · 2H₂O was examined by means of both isothermal and dynamic gravimetries. These dehydration processes proved to be controlled by a random nucleation and its subsequent growth mechanism. No significant kinetic isotope effect was seen in these dehydration stages. It seems that there exists a kinetic compensation effect between the hydrate and its deuterium analog, if any isotopic differences in activation energy and frequency factor could exist.     

Double focus interferometers and errors the influence of their sample setting errors

Double Focus interferometers are attractive for reducing the influence of ambient conditions due to their common-path configuration. This paper describes the influence of sample setting errors in these interferometers. They have been divided into two types, i.e. the normal illumination type and the oblique illumination type. For each type, an equation of the measurement error due to sample setting error has been derived with Gaussian optics. The measurement error of the normal illumination type becomes a parabolic function of the position on the sample surface. The derived error equations have been verified by ray tracing and by experiment. The error of the oblique type is smaller than that of the normal type.     

Deuterium isotope effects in the thermal dehydration of K2Mg(SO4)2 · 6H2O

Deuterium isotope effects in the thermal stability, enthalpy change, and kinetic parameters were examined by means of TG-DSC recorded simultaneously for the dehydration stages of

The thermal stability and enthalpy change for the hydrate were smaller than those for its deuterium analog in stage (1). In addition, the rate constant for the hydrate was larger than that for the deuterate in this stage. As for stages (2) and (3), any isotope effect in these parameters was not recognized in practice. The correlation of these isotope effects observed in stage (1) is briefly discussed     

Preparation of Metal-free phthalocyanine using the benzenetellurolate ion

Metal-free phthalocyanine was prepared from o-phthalonitrile using the benzenetellurolate ion in ethanol. Furthermore, the yield of metal-free phthalocyanine using the benzenetellurolate ion was compared with that using the benzeneselenolate ion or the benzenethiolate ion.     

The mechanism of elimination of an H2O molecule in desmethylencecalin under electron impact

The mass spectrum of desmethylencecalin has been measured and a fragmentation mechanism for the loss of a water molecule from the [M? CH₃]⁺ ion is proposed on the basis of isotope labelling and metastable peak observations. The eliminated water has been shown to involve the carbonyl oxygen and hydrogen atoms of the hydroxyl and acetyl groups.     

Nuclear quadrupole resonances of α-(CH3)2 TeX2 (X=Cl, Br, I) and (CH3)2 TeI4

NQR spectra were observed for α-(CH₃)₂ TeX₂ (X=Cl, Br, I) and (CH₃)₂ TeI₄ at various temperatures. The two ⁸¹Br NQR lines were observed above 110 K in α-(CH₃)₂TeBr₂. The characteristic temperature dependence of the ¹²⁷I NQR line in α-(CH₃)₂ TeI. can be explained by the 3c—4e bond of the linear I---Te---I group. The positive temperatures dependence of the lowest ¹²⁷I NQR line in (CH₃)₂TeI₄ is discussed on the basis of the electron population calculated from Townes—Dailey treatment.     

Radiometric redox titration of antimony(III) with potassium iodate

The redox titration of antimony(III), labeled with¹²⁵Sb(III), by potassium iodate was radiometrically investigated using the burette method and the standard series method. The stoichiometry of the redox process was determined. The redox valence (the number of equivalents per mol) of potassium iodate for the oxidation of antimony(III) to antimony(V) was found to be 6, differing from the results obtained using the usual visual indicator method, where the value was shown to be 4. This disagreement in the equivalents of potassium iodate for the oxidation of antimony(III) is discussed.