Elektronenspinresonanz- und optische Untersuchungen zur FarbzentrenreaktionF⇄F′ in KCl-Kristallen

Simultaneous measurements of optical absorption and electron spin resonance of additively colored KCl crystals have been carried out during the optical bleaching ofF-centers at ?90°C. TheF-center resonance signal does not change in its significant properties e.g. line shape, line width,g-value, and saturation behavior, but it decreases proportional to the decrease of the opticalF-center absorption band. No ESR-signal due to theF′-center could be observed. The time dependence of theF?F′-center conversion has been investigated by ESR and optical measurements. It does not give any indication of a paramagnetism of theF′-center, too. The kinetics of the thermal decay of theF′-center at ?90°C have been studied. One can interpret the time dependence of this process, if one assumes that the mean lifetime of anF′-center depends on the distance of the nearest halogen ion vacancy. The expectation of life of theF′-centers therefore increases during the thermal decay, as the mean distance between remainingF′-centers and vacancies increases.     

Schrödinger equation in multiply connected spaces and phase optics

The magnetic vector potential\(\vec A\) in a field free spaceR ₀ cannot be removed by gauge transformations in general, ifR ₀ is multiply connected.Aharonov andBohm ¹ have noticed recently that\(\vec A\) therefore should have more physical meaning than only to give the magnetic field by differentiation. They could show that\(\vec A\) inR ₀ may influence the phase ofSchrödinger'sψ-function in an observable manner. We want to point out here that this influence can be expressed in a simple, general form: “A closed magnetic field line operates uponψ like ae Φ/?-phase-shifter placed on any area bounded by the field line.” Surface like phase shifters are familiar in phase optics. There exists a narrow relationship between electron scattering at magnetic fields and some special problems of phase optics. An electron phase contrast microscope is discussed.     

Zur Theorie der infinitesimalen Holonomiegruppe in der Allgemeinen Relativitätstheorie

Starting from the infinitesimal holonomy groupH _i of aV ⁴, (+++?) the spinholonomy group\(\tilde H_i \equiv \bar \sigma ^1 (H_i )\) defined by the covering isomorphism\(\sigma :G \to L_ + ^ \uparrow \) is introduced. In Einstein-spaces we may replace its real Lie-algebra by a complex one. With the complex calculus we may reproduce the results ofSchell, Goldberg andKerr with very much simplified proofs. A theorem on non-empty Einstein-spaces is given. In part 4 we prove a theorem on the connection between theH _i -behaviour of a vector (spinor) and its covariant derivative in aV ⁴. With its help we get in a simple manner the metiics of aV ⁴ with givenH _i and Dim (H _i ) <6; our results agree with those given byGoldberg andKerr, Cahen andDebever. Finally we make some new statements on imperfect holonomy groups.     

Einfluß der Pion-Pion-Wechselwirkung auf Pion-Nukleon-Streuphasen

The isospin dependent part of theS-wave pion-nucleon amplitude is calculated according to the CGLN approach, but recoil and projection on the partial waves are treated exactly. Then the difference against the experimental data is approximately a constant up to 100 MeV and amounts to 1/3 of the total value. It is shown, that at low energies the main corrections of the CGLN equations are taken into account by a subtraction of theπ+π→?+\(\overline \Re \),J=I=1 amplitudesf _± ¹ (t) as proposed byMandelstam andFrazer. Calculations have been done forS, P andD pion-nucleon amplitudes. The main result is a prediction of theS-wave amplitude obtained without adjusting free parameters up to 100 MeV. The relations of this method to the equations derived byBowcock, Cottingham andLurié according to the Cini-Fubini approach are discussed.     

Mechanisms of ionization of <Emphasis Type="Italic">F</Emphasis><Subscript>2</Subscript>-centers in laser media on the basis of LiF crystals

F₂ color centers with a superhigh concentration (5000-cm^–1 absorption coefficient at 450 nm) were formed by high-density electron beams in a layer of LiF crystals of micrometer thickness. The F₂-centers excited by high-power nanosecond wide-band optical pulses (the “soft” pumping regime) efficiently amplified the laser radiation and showed high stability under these conditions. A low stability of F₂-centers to laser radiation (the “hard” excitation regime) is explained by the dissociation of (F ₂ ⁺ , F^–) pairs induced by two-step ionization of F₂-centers: (2hν > 4.5 eV) → F₂ → (F₂)* → F ₂ ⁺ + e; F + e → F^–; F ₂ ⁺ + F^– → 3F.     

Relativistic Slater's integrals for theK andL shells

TheZ-dependent form of theSlater's integrals for electrons in theK andL shells is studied by expanding the relativistic hydrogenic radial wave functions in the manner explained byLayzer andBahcall. When screening is not taken into consideration, theseSlater's integrals can be put in the form AZ(1+a Z²) wherea is positive for all integrals considered except G¹(1s, 2p) and G²(2¯p, 2p). Values ofA anda are given.     

Vibrational analysis of the (B 2 П→X 2 П) system of NS

A few red degraded bands attributable to NS have been reported earlier byFowler andBarker, Dressler andBarrow et al, and they occur in the same region (2300 to 2700 Å) as the bands of the known systems (C ² ∑ ⁺?X ² П) and (A ² Δ?X ² П). Measurements made on the heads of some of these weak bands ledBarrow et al. to believe that these bands may form a system analogous to theβ-system of NO and be due to a² П-² П transition. The spectrum of NS has now been studied in a little more detail by means of an uncondensed discharge through dry nitrogen and sulphur vapour in the presence of argon and thirty three bands belonging to this system have been recorded in the region 2280 to 2760 Å. It has been found possible to represent the band heads by means of the equation

$$^v {\text{head}} {\text{ = }} \left. {_{43182 \cdot 5}^{{\text{43311}} \cdot {\text{5}}} } \right\}_{ - [1219 \cdot 20(v'' + \tfrac{1}{2}) - 7 \cdot 48(v'' + \tfrac{1}{2})^2 ].}^{ + [761 \cdot 04(v' + \tfrac{1}{2}) - 5 \cdot 10(v' + \tfrac{1}{2})^2 ]}$$     

Volumenänderung durch Gitterverzerrung um ein F-Zentrum in Alkalihalogenidkristallen

The lattice-distortions in the vicinity of anF-centre in alkalihalide crystals and the volume change arising from the lattice distortions around this defect are being calculated. Only theF-centre ground state is considered and the effect of lattice vibrations is neglected. The interaction of theF-electron with the ions is described in terms of effective potentials, and a vacancy-centered wave function is calculated for theF-electron. In calculating the lattice distortions, an approximative procedure is adopted in which only the ions in the vicinity of anF-centre receive an atomistic treatment whereas the remainder of the crystal is treated as an elastic continuum. The volume change caused by the lattice distortions around anF-centre is calculated, using a method ofFischer andHahn which does not require an exact knowledge of the asymptotic strainfield around the point defect. The ions of the first, second and third shell around theF-centre-vacancy are found to be displaced in an outward direction. For the volume-change perF-centre the following values were obtained: 0.26a ³ in NaCl, 0.31a ³ in KCl and 0.35a ³ in KBr,a being the interionic distance. In order to check the validity of some of the approximations employed in the calculations, the volume changes caused by substitution of alien alkali- or halideions are computed and are found to be in good agreement with experimental data.     

M-Zentrenbildung in röntgenbestrahltem KCl

The equilibrium betweenF- andM-center concentration in KCl after X-irradiation at temperatures between 77 °K and 298 °K has been studied. At low temperatures (<200 °K) onlyF-centers which are formed statistically as nearest neighbours give aM-center. At higher temperaturesF-centers within a certain sphere of interaction with a radiusr formM-centers. The temperature dependance of this radiusr has been evaluated. The equilibrium constantK depends on the temperature in the form K=K₀exp(-Q/kT). The activation energy was determined to be Q=(0.5±0.1) eV.     

Untersuchung des ZerfallsBi^{212} (ThC)\xrightarrow{\beta }Po^{212} (ThC')\xrightarrow{\alpha }Pb^{208} (ThD) durch (γ, α)-Koinzidenzen

Theγ-spektrum of Po²¹² (ThC′) has been measured by (γ, α)-coincidences with a fast-slow coincidence apparatus. The results are in excellent agreement with the conversion lines found by theLatyshev group. The absoluteγ-intensities have also been determined in order to get spins and parities of the levels by calculating the absolute conversion coefficients. Theβ-intensity leading to the exited states of Po²¹²(ThC′) is estimated to be about one third of that measured byBurde andRozner by (β, α)-coincidences. Threeγ-lines measured byChinaglia andDemichelis by (γ, α)-coincidences do not agree with our results. The 2⁺ assignment of the first exited state is now well established, but for the other levels in the decay scheme there is still some uncertainty concerning spin and level assignment.     

On the connection between the decaysπ 0→2γ andπ +→e++υ+γ

A result discovered byVaks andIoffe is newly derived using reduction technique and G-invariance only. It has some consequences concerning the decaysπ ⁰→2γ andπ ⁺→e⁺+υ+γ and various coupling constants of the? and ω particle.     

Octupole vibrations of deformed nuclei

The octupole vibrations of deformed nuclei are studied. A strong coupling between the harmonic octupole vibrations and the quadrupole ellipsoid is assumed. This interaction gives rise to a splitting of octupole bands with different projection quantum numberK. TheE1-transitions of the octupole states are explained within the frame of the Dynamic Collective Theory ofDanos andGreiner by calculating the Coulomb interaction between octupole vibrations and giant resonances. Furthermore, theE2- andE3-transitions of the octupole states are studied. The spectrum of W¹⁸² is investigated in detail. A fair agreement between theory and experiment is obtained. Predictions for the octupole spectra of Sm¹⁵² and Gd¹⁵⁶ are given.     

Measurement of the Lamb shift 42S1/2-42P1/2 of the helium ion

Helium ions were produced in then=4 states by electron collisions with ground state atoms, resulting in simultaneous ionization and excitation. Dipole transitions between the Zeeman levels of the states 4² S _1/2 and 4² P _1/2 were induced by a microwave electric field. The intensity of the emitted Fowlerα line 4686 Å, corresponding to transitions from then=4 to then=3 states was then reduced by about 3%. From the measurements, a value of the Lamb shiftδ=1751±25 MHz was obtained, compared with the theoretical valueδ=1768.23±0.55 MHz, and the results ofLea, Leventhal andLamb ofδ=1765±20 MHz.     

Vergleich der Photoerzeugung von π0 am Proton mit der Voraussage nach der Dispersionstheorie

The real parts of the photoamplitudesE 1S _1/2,M 1P _1/2,M 1P _3/2 have been calculated from the angular distribution of the reactionγ+p→p+π⁰ recently measured byGoldansky et al. at 160 to 240 MeV. One of the solutions fits pretty well to the theoretical prediction for theM 1P _3/2-amplitude according to the dispersion method ofChew, Goldberger, Low andNambu. There is a discrepancy forM 1P _1/2 ifα ₁₁ is taken from the effective range formula, but the positive values ofα ₁₁, necessary to give agreement, are not excluded by the results of the phase shift analysis, especially sincePontecorvo et al. have recently found positive values at higher energies. The prediction for the real part of theE 1 S_1/2-amplitude agrees with the experimental data, if pretty large recoil corrections are added which had been neglected byChew et al.     

Experimentelle Untersuchung zur Fluktuation der Wirkungsquerschnitte für die Reaktionen F19(n,2n)F18, Al27(n,α)Na24 und Cu65(n,2n)Cu64

Using the activation method investigations on the fluctuation of the total reaction cross sections for the reactions F¹⁹(n, 2n)F¹⁸, Al²⁷(n, α)Na²⁴ and Cu⁶⁵(n, 2n)Cu⁶⁴ were performed in the 14 MeV region under similar conditions as in the experiments reported byStrohal et al. and byCsikai on the same subject. In disagreement to the results of these authors no considerable fluctuation amplitudes were found.     

L/K-Einfangverhältnis von65Zn

A multiwire proportional counter was constructed to measureL/K-capture ratios. The length of the counter is 90 cm, the diameter 14 cm, and it works with pressures from 1 to 6 atm. — The counter was proved by measuring theL/K-capture ratio of³⁷Ar. The result obtained is 0,098±0,003, in agreement with the calculated ratio 0,100 ofBahcall and the results of many other measurements with multiwire proportional counters. — Gaseous radioactiv Zincdiethyl was the substance to determine theL/K-capture ratio of⁶⁵Zn. The result obtained is 0,111±0,006, in agreement with the calculated ratio 0,109 ofBahcall, while 0,119±0,007 measured with a multiwire proportional counter bySantos Ocampo andConway is somewhat above the calculated ratio.     

Behaviour of some faintK β for elements As(33) to Ru(44)

1. 1.
   It has been shown that the semi-Moseley graphs for theβ ₈,β ₇,β ₆,β ₅,β ₄,β ^?,β ₁₁ ^? andβ ₀ in theK-series for elements over the rangeZ=33 toZ=44 reported byHulubei, Cauchois andManescu become remarkably regular when referred toα ₁ instead ofβ ₁ as the parent line.     
   
   

Pion-pion interaction andK 2x03C0;x03C0;x03C0;-decay

The enhancement of theK _2π ⁺ -decay compared to theK _2π ⁰ -decay is discussed on the basis of the\(|\mathop {\Delta {\rm I}}\limits^ \to | = \tfrac{1}{2}\)-rule. The enhancement factor is calculated by dispersion methods which yield an expression depending only on the phase shift of the two pion system in theJ=0,I=0,2 state. This expression has been studied in the framework of simple models for the two-pion interaction in order to obtain a survey of the possibilities for the cause of the anomalous large ratioK _2π ⁺ /K _2π ⁰ . Only characteristic cases have been considered and, as far as possible, experimental results of theπ-π-interaction are taken into account.     

Paramagnetische Resonanz von Zentren mit den Symmetrienn,\bar n undn/mundn/m

The consequences of applying the spin-Hamiltonians ofAbragam andPryce to paramagnetic centers with the low symmetriesn,\(\bar n\) andn/m(C _n ,C _nh ,S _n ) are examined. The asymmetry of theg- and the hfs-tensors, described in an earlier paper, is considered in this context. The point is that for the symmetries under consideration the coordinate systems are not determined by the symmetry elements. For this reason it is possible to introduce separate coordinate systems for the magnetic field, the electron spin and the spins of the nuclei and this allows the symmetrisation of the tensors under certain conditions. This procedure also leeds to an understanding of the independent parameters found in the Hamiltonians. Ambiguities between the spin-Hamiltonians and the esr-spectra indicate the limits of theAbragam andPryce formalism. The application of the theory to paramagnetic centers under the influence of external, electrical fields is discussed and reveals interesting aspects.     

Diekll-Auger-Spektren von Eisen und Vanadium

The relative intensities of theKLL-Auger transitions of Fe (Z=26) und V (Z=23) were measured with an iron free, double focusing β-spectrometer. The results obtained are in good agreement with those measured bySokolowski andNordling forZ=29 andZ=32. This confirms the discrepancies between the nonrelativistically calculated intensities and the experimental values in the region of lowerZ. A summary is given about all known measurements of theKLL-Auger intensities. Also theKLL∶KLX-ratio of Fe was measured to be 1·0∶(0·19±0·01). The energy of the 14·4-keVγ-transition of Fe⁵⁷ was evaluated to be (14389±6) eV.