Showing papers by "Fritz Haber Institute of the Max Planck Society published in 1974"
TL;DR: In this article, the potential difference between monolayer and bulk deposition is closely related to the difference in the work functions of substrate and deposit, causing a partial charge of the adatoms.
500 citations
01 Oct 1974
TL;DR: In this paper, a blocking region of only about 3 V is found in high-dose ZnO-electrodes, where the field emission of valence electrons into the conduction band is attributed to the generation of holes.
Abstract: Highly doped ZnO-electrodes show a blocking region of only about 3 V. Above this region anodic breakdown currents set in which rise steeply with increasing potentials. The currents are attributed to the generation of holes by field emission of valence electrons into the conduction band. The generation of holes is shown by surface reactions, like the oxidative lattice decomposition, or by the current multiplication in particular oxidation reactions of organic substances which are well known as being caused by holes. Another indication of hole generation is the light emission during anodic breakdown currents caused by recombination of holes with electrons.
On the polar ZnO surfaces (〈0001〉 and 〈0001〉 surface) considerable differences are observed in the anodic currents and in the composition of reaction products.
Hochdotierte ZnO-Elektroden zeigen einen anodischen Sperrbereich von nur etwa 3 V Ausdehnung. Oberhalb dieser Spannung treten Durchbruchstrome auf, die mit wachsendem Potential stark ansteigen. Diese Strome werden durch die Generation von Defektelektronen mittels Feldemission von Valenzelektronen in das Leitungsband verursacht. Die Generation von Defektelektronen wird durch Grenzflachenreaktionen nachgewiesen, die bekannt dafur sind, das sie durch Defektelektronen ausgelost werden. Diese sind die oxidative Zersetzung des ZnO-Kristalls sowie die Stromvervielfachung bei der Oxidation bestimmter organischer Substanzen. Auserdem beweist die Lichtemission wahrend der anodischen Durchbruchstrome eine Rekombination von Defektelektronen mit Leitungselektronen.
An den polaren ZnO-Oberflachen (〈0001〉- und 〈0001〉-Flache) treten bemerkenswerte Unterschiede in den anodischen Stromen und der Zusammensetzung der dabei gebildeten Reaktionsprodukte auf.
92 citations
TL;DR: The roughness-aided optical excitation of surface plasmons produces pronounced peaks of the photoemission and photooxidation yields at a silver-electrolyte interface which cannot be observed in vacuum studies as mentioned in this paper.
61 citations
TL;DR: Two-dimensional models for the development of the dissolution forms of single crystal spheres are presented in this article, where the dissolution form faces consist of microscopical or sub-microscopical terraces of equilibrium form faces or the velocity of dissolution is determined by the detachment of lattice elements from the half-crystal position.
54 citations
50 citations
TL;DR: The elektronenmikroskopische Untersuchung von hydratisiertem biologischen material in feuchten Kammern bringt unvermeidliche, schwere Objektschadigungen mit sich Deshalb wurden diese Objekte tiefgekuhlt untersucht Das eingefrorene Praparat wurde dazu ohne Unterbrechung der Tiefkuhlung und ohne Aufwacbsen e
49 citations
TL;DR: X-ray diffraction patterns suggest that the microfibrils in the collagen of native rat tail tendon are eight-stranded ropes, quarter staggered and packed together in an orthorhombic lattice with paracrystalline (liquid-like) distortions between adjacent tropocollagen molecules.
43 citations
TL;DR: In this paper, the authors investigated the influence of molecular diffusion on the ortho-para conversion in solid hydrogen at 12, 4.2, and 1.57 K in long-term experiments up to 1200 h.
Abstract: The ortho-para conversion in solid hydrogen is investigated at 12, 4.2, and 1.57 K in long-term experiments up to 1200 h. The results are discussed in the light of the influence of molecular diffusion on the conversion rate. At 4.2 and 1.57 K, the conversion rate shows that the diffusion coefficient is $D\ensuremath{\approx}{10}^{\ensuremath{-}20}$ ${\mathrm{cm}}^{2}$ ${\mathrm{sec}}^{\ensuremath{-}1}$. This value is much larger than those predicted from an extrapolation of experimental results at higher temperatures and from recent theoretical predictions. At 1.57 K, an increase of the conversion rate with decreasing $o\ensuremath{-}{\mathrm{H}}_{2}$ concentration is observed. Calculations show this increase is due to clustering of $o\ensuremath{-}{\mathrm{H}}_{2}$ molecules caused by electric quadrupole-quadrupole interactions between them. The estimated diffusion rate is consistent with that found previously from the rate of clustering.
37 citations
TL;DR: In this article, the decay time, temperature dependence and spectrum of fluorescence emission of vacuum-deposited tetracene films were measured and it was concluded that the emitting species is a molecular pair in sandwich configuration.
30 citations
TL;DR: In this article, the fluorescence emission spectra and fluorescence decay times of amorphous films prepared by evaporation of a number of aromatic hydrocarbons on to a substrate cooled with liquid nitrogen were measured.
26 citations
TL;DR: In this article, a 10-fold hot stretched (80 °C) linear polyethylene (PE) was prepared for high precision AEG-Guinier-Jagodzinski camera by cutting into 0.1 mm thick slices.
Abstract: 10-fold hot stretched (80 °C) linear polyethylene (PE) was prepared for high precision AEG-Guinier-Jagodzinski camera by cutting into 0.1 mm thick slices. Now the line profiles of allhk0-reflections were clearly separated and analysed using the paracrystalline theory. The slices were first annealed at 120 °C and then irradiated under vacuum with 10, 100 and 300 Mrad ofCo
60. The lattice parameters increase remarkably in full agreement withKobayashi. The paracrystallineg-values increase mostly orthogonal to the (110) net planes and no microstrains are generated. The average size of the microparacrystallites increases at least until 100 Mrad. In connection with former experiments about the affine transformation of molten PE we conclude that the crosslinks are produced predominantly within the paracrystallites. A model is discussed.
TL;DR: In this article, the isosteric energy of adsorption on single crystal faces can be measured, if the coverage is kept constant on controlling the field electron currents, and the results indicate a relation between the adsorment states and the structure of each face.
TL;DR: In this paper, a mass spectrometer was used to detect positive ions with a steady state field of > 0.1 V/A with a sensitivity of −1 and at temperatures between 80 °K and 425 °K.
TL;DR: In this article, a new statistical theory leads to a simple relation between the crystallinity and the branching ratio e for polyethylene (PE) cold drawn to the natural draw ratio.
Abstract: A new statistical theory leads to a simple relation [eq. 3] between the crystallinity and the branching ratio e for polyethylene (PE) cold drawn to the natural draw ratio. Three assumptions are made:
1)
The branches all are incorporated in the amorphous phase,
2)
they are distributed randomly along the chain and
3)
the sample tends to obtain the highest possible crystallinity during the stretching process.
TL;DR: In this article, a beam of molecular sulfur S2 is produced from solid Ag2S in an electrochemical source and directed unto a tungsten field emitter, where the field ionization and field desorption of sulfur is investigated between 150 and 500 °K and at impingement rates up to levels where the formation of multilayers of sulfur on Tungsten occurs.
TL;DR: In this article, a series of nuclear magnetic resonance spectra (NMR) of differently treated polyethylene (PE) and paraffin samples was analyzed unequivocally as the sum of four standard functions which are attributed to four components, α, β1, β2, and γ, of increasing proton mobility.
Abstract: A systematic investigation of a series of nuclear magnetic resonance spectra (NMR) of differently treated polyethylene (PE) and paraffin samples, indicates that all observed spectra can be analysed unequivocally as the sum of four standard functions which are attributed to four components, α, β1, β2, and γ, of increasing proton mobility. In some spectra most of the components are clearly separated from each other. The shape of their derivatives is therefore directly measurable and symmetric for the α-component. For β1 the derivative is that of a Gaussian and for γ that of a Lorentzian function. β2 alone is not directly observable but appears as a remainder in the spectra of melt-crystallized PE. It exhibits the shape of the derivative of a Lorentzian function, too. The basic hypothesis is that each of these four components maintains his characteristic shape even if they overlap each other. The line widths ΔH are: 13,2 to 17,9 Gaus (1 Gaus = 10−4Vs m−2), 3,0 to 6,0 Gaus, 0,85 to 1,2 Gaus, and 0,04 to 0,18 Gaus, depending on the history of the sample. The α-component is assigned to protons in the microparacrystalline phase (regular backfolding included), fixed chain ends and tight tie-molecules. In hotstretched PE the latter enlarge the α-component by 4% without changing the “crystallinity” measured by the density. γ is assigned to longer chain ends undergoing micro-Brownian motion. The more regular the lamella surface, the smaller is the contribution to the β1 and β2 component.
So-called single crystals of PE e.g. have only 0,02% γ, which increases during melt-crystallization to ca. 0,1% (sample MPE 5). Its extremely high value of 0,4% in all drawn samples (DPE) is attributed to an enlarged number of longer mobile endsegments generated by chain scission. β1 is attributed to less mobile chain ends, chains in lateral grain boundaries, defects within the paracrystals, chainfolds and tie-molecules in the “amorphous” parts which are of great importance for the mechanical properties. If the component β1 e.g. is smaller than 15%, melt-crystallized PE (MPE) is always brittle. When the melt is stirred, β1 in the MPE reaches values up to 19%. The tensile strength then is larger. In extended chain crystals (ECC) β1 is reduced to about 10% of the MPE-value. This may indicate that about 10% of the ECC still have the folded structure. This is underlined by the fact that MPE alone has a remarkable β2-component from segments more mobile than β1 which is reduced also to about 10% in ECC. The β2-component is attributed to loose loops and loose connecting molecules, which connect neighbouring paracrystals.
Eine systematische Untersuchung der magnetischen Kernresonanzspektren (NMR) verschieden behandelter Polyathylen- und Paraffinproben zeigt, das alle beobachteten Spektren eindeutig als Summe von vier Komponenten analysiert werden konnen. Jede dieser Komponenten wird durch eine charakteristische Standardfunktion dargestellt. In manchen Spektren sind die Komponenten klar getrennt voneinander erkennbar. Die Gestalt ihrer Differentialquotienten ist also direkt mesbar und ist symmetrisch fur die Komponente a geringster Protonenbeweglichkeit. Die Komponente β1 stellt sich als Ableitung einer Gausfunktion heraus, γ als Ableitung einer Lorentzfunktion. Die Komponente β2 allein ist niemals direkt beobachtbar, sondern erscheint, falls uberhaupt, als Restbetrag in schmelzkristallisiertem Material. Auch sie hat die Gestalt der Ableitung einer Lorentzfunktion. Die Grundidee der vorgenommenen Analyse der Spektren ist, das jede dieser 4 Komponenten ihre charakteristische Gestalt behalt, gleichgultig, ob die Komponenten sich uberlappen oder nicht. Die Linienbreiten ΔH sind dann fur α, β1, β1, β2 und γ: 13,2 bis 17,9 Gaus, 3,0 bis 6,O Gaus, 0,85 bis 1,2 Gaus und 0,04 bis 0,18 Gaus, wobei der spezielle Wert innerhalb jedes Intervalls von der Vorgeschichte der Probe abhangt. Die α-Komponente wird den Protonen in den Mikroparakristallen einschlieslich den regelmasigen Kettenruckfaltungen, fixierten Kettenenden und steifen Kettenbrucken zugeordnet. In heis verstrecktem Polyathylen (PE) vergrosern letztere die α-Komponente um 4%, ohne die Dichte der Proben zu andern. γ wird den losen Kettenenden mit Mikro-Brown'scher Bewegung zugeordnet. Je regelmasiger die Oberflache der Kristalllamellen, desto schwacher ist die β1- und β2-Komponente.
Sogenannte Einkristalle von PE haben z. B. nur 0,02% γ-Komponente, die sich beim Schmelzkristallisieren auf etwa 0,1% erhoht (Probe MPE 5). Der extrem hohe Wert von 0,4% in allen verstreckten Proben (DPE) wird langeren beweglichen Kettenenden und einer vermehrten Zahl von Kettenenden zerrissener Ketten zugeordnet. Weniger beweglich sind die Kettenenden der Kornponente β1, zu der auch Ketten in lateralen Korngrenzen und Kettensegmente in Storstellen innerhalb der Mikroparakristallite gehoren. Auserdem tragen hierzu unregelmasige Kettenruckfaltungen der Molekule bei, die von Parakristall zu Parakristall laufen und in den sog. „amorphen” Bereichen der Probe liegen. Dieser Protonenanteil ist von groser Bedeutung fur die mechanischen Eigenschaften. Wenn die Komponente β1 z. B. kleiner als 15% ist, dann ist das entsprechend schmelzkristallisierte PE (MPE) bruchig Wenn die Schmelze geriihrt wird, kann β1 Werte bis zu 19% erreichen. Die Zugfestigkeit ist dann besonders gros. Im verstreckten Kettenkristall (ECC) ist β1 auf 1/10 des MPE-Wertes abgesunken. Dies kann man dadurch erklaren, das hier immer noch 10% der Probe Faltstruktur haben. Ein weiterer Beweis dafur ist auch, das nur MPE eine merkliche β2-Komponente noch hoherer Protonenbeweglichkeit als β1 hat; auch sie wird in ECC auf 10% reduziert. Die β2-Komponente wird ganz losen Ruckfaltungen und unregelmasig locker liegenden Molekulen zugeschrieben, die benachbarte Parakristallite verbinden.
TL;DR: In this paper, weitwinkelreflexe zeigt teilweise eine Aufspaltung in Vielfache einer kleinsten Kristallitgrose.
Abstract: Fur verschiedene Zelluloseproben wurden mittels Rontgenweitwinkelstreuung die mittleren lateralen Kristallitgrosen und ihre Gestaltellipse in der Ebene senkrecht zur Kettenrichtung bestimmt. Die Gausanalyse der Weitwinkelreflexe zeigt teilweise eine Aufspaltung in Vielfache einer kleinsten Kristallitgrose. Dies wird auf teilweise Rekristallisation zuruckgefuhrt. Die Gausanalyse der kontinuierlichen Kleinwinkelstreuung liefert in allen Fallen gleichfalls Vielfache einer kleinsten Einheit. Zeigt der Weitwinkelreflex keine Aufspaltung, kann das Kleinwinkelergebnis nicht durch Rekristallisation, sondern durch einfache Clusterbildung erklart werden.
DOI•
01 May 1974TL;DR: In this paper, the anodic behavior of highly doped ZnO(In) electrodes (ND = 1019 2020 cm−3) was studied in aqueous electrolytes.
Abstract: The anodic behaviour of highly doped ZnO(In) electrodes (ND = 1019 2020 cm−3) was studied in aqueous electrolytes. Addition of the reduced species of inorganic redox couples (I−, Fe2+) to the electrolyte causes oxidation currents at a bandbending above 1 eV in the otherwise blocking region of the electrode. The reverse reaction is also possible where the oxidized species of a suitable redox couple (e.g. Ir(Cl)62-) is reduced by conduction electrons. The corresponding bandbending precludes the overcoming of the potential barrier by thermal activation. Electrons can, accordingly, tunnel through the space charge barrier of such highly doped ZnO electrodes in both directions. Sensitizing dyes (rhodamine B, crystal violet) are also oxidized at such electrodes in the absence of illumination by tunnelling electrons. The oxidation of organic reducing agents (e.g. hydroquinone) which can act as “supersensitizers” can, however, only be achieved after addition of traces of dyes.
Das anodische Verhalten von hochdotierten ZnO(In)-Elektroden (ND = 1019 1020 cm−3) wurde in wasrigen Elektrolyten untersucht. Der Zusatz der reduzierten Form anorganischer Redoxsysteme (J−, Fe2+) zum Elektrolyten ruft oxidative Strome im Sperrbereich der Elektroden bei einer Bandaufbiegung oberhalb 1 eV hervor. Auch die Umkehrung dieses Prozesses ist moglich. Die oxidierte Spezies geeigneter Redoxsysteme (z. B. (Ir(Cl)62-) kann durch Leitungselektronen reduziert werden. Dabei liegt eine Bandaufbiegung vor, die eine Uberwindung der Potentialbarriere durch thermische Aktivierung von Leitungselektronen ausschliest. Die Raumladungsbarriere so hoch dotierter Zinkoxidelektroden kann demnach von Elektronen in beiden Richtungen durchtunnelt werden.
Farbstoffe (Rhodamin B, Kristallviolett), die als Sensibilisatoren wirken, werden ebenfalls an solchen Elektroden ohne Beleuchtung durch tunnelnde Elektronen oxidiert. Dagegen ist die Oxidation organischer Reduktionsmittel, die als Ubersensibilisatoren Verwendung finden (z. B. Hydrochinon). erst nach Zusatz von geringen Mengen Farbstoff moglich.
TL;DR: In this paper, the structure of extended native collagen was discussed and it was and still remains an open question if these kinks, are already established in the unstretched sample or are only formed under stress.
Abstract: In a previous paper the structure of extended native collagen was discussed. It was and still remains an open question if these kinks, are already established in the unstretched sample or are only formed under stress. If so, their production is explained in this paper by a heterogeneous expansion of the protofibrils similar as in elastomers. All 135 A one meets “amorphous” non helical regions where the polypeptide-chains are more disordered as in the paracrystalline triple helical domains. In synthetic elastomers these parts of a molecule are called “soft segments”. If this expansion solely takes place in the “amorphous” ranges and if these zones are 20 A long, then the earlier published (observed) data of the kink model quantitatively can be explained by expanding the protofibrils 11% in the “amorphous” ranges. An example is given, where the density of the “amorphous” region does not change during stretching. The expansion by 11% takes place because the polypeptide chains within the triple helices are straightenend. They run more or less parallel to the screw lines of the triple helix through this zone. The long period only increases by 0.3%. If the density of the “amorphous” regions diminishes more than a few percent, an appreciable increase of the long period would happen. This contradicts the experiments. The mean density does not change in the “amorphous” regions during stretching. Most of the macroscopic elongation takes place outside of the fibrils with the 670A periodicity. Only about 1/7 of it is elastic and is produced by the restoring force of network peptides aligned in between adjacent octafibrils and bundles of them. The important role of these “intermicellar” molecules and similarities with the affine transformation in synthetic high polymers is discussed. The model of staggered collagen molecules ofSchmitt (1956) which explains the 670 A-period in quite another way cannot explain an elastomeric production of tilted paracrystalline triple helical regions under strain.
TL;DR: In this article, a small angle X-ray diffraction study of poly(oxydecamethylene) [poly(decamylene oxide)] is presented regarding the influence of the chemical nature of the macromolecule on the fold length value.
Abstract: The present paper deals with a small angle X-ray diffraction study of poly(oxydecamethylene) [poly(decamethylene oxide)] (1) regarding the influence of the chemical nature of the macromolecule on the fold length value. Four fractions of 1 with different molecular weights, were crystallized and the highly diluted solutions of the crystals were deposited in layers just a few microns (μm) thick. These layers were investigated by means of X-ray diffractometry. In all fractions the X-ray long spacing, L, exhibits characteristic values which differs in the ratio of monomeric lengths. The crystal thickness predominantly corresponds to n=2 and 3 times half the value of the unit cell (13,75 A), for crystallization temperatures Tc≤20°C. At higher temperatures these values increase to n=6. However, at Tc≈50°C n changes to n=7 or 8 and recovers the value n=6 at higher crystallization temperatures if the substance is still able to crystallize at these temperatures. The multiples of 13,75 A obtained can be explained by a specific lateral packing of stems according to a proposed model which preserves the unit cell, excludes the oxygen atoms from the folds, and favours the idea of a regularly folded surface layer (4–5 atoms per fold, 2–3 A thick) and of an ordered three dimensional suprastructure of oxygen atoms within the lattice. Similarly, the increase of the fold length on annealing occurs in steps equal to a whole number of repeating units along the molecular chain.
In der vorliegenden Untersuchung werden Rontgenkleinwinkelmessungen an Poly(oxydecamethylen) [Poly(decamethylene oxide)] (1) in Abhangigkeit von vier verschiedenen Molekulargewichten mitgeteilt und der Einflus der chemischen Konstitution der Makromolekule auf die Faltungslange diskutiert. Hierzu wird eine neue Mikrotechnik angewandt, bei der nur wenige Tropfen der hochverdunnten Kristall-Losung auf eine Glasplatte gebracht werden. Die wenige Mikron (μm) dicken Belage werden in Reflexionsstrahlung untersucht. Aus der Langperiode kann in Abhangigkeit von der Kristallisations- und Temper-Temperatur die Dicke der Kristall-Lamellen und der dazwischenliegenden Ruckfaltungsbereiche errechnet werden. Die Kristalldicke kommt in allen Fraktionen in ganzzahligen Vielfachen n von der Monomerkettenlange (13,75A) vor; n=2 und 3 treten fur Kristallisationstemperaturen Tc≤20°C bevorzugt auf, bei hoheren Temperaturen verschwinden sie und machen Faltlangen von n=6 Platz. In einem noch nicht naher untersuchten Temperaturbereich bei Tc ≈50°C verwandelt sich die Kristalldicke zu n = 7 bzw. 8, um bei hoherer Temperatur wieder auf n=6 abzusinken, falls die Substanz hier noch kristallisieren kann. Die auftretenden Vielfachlangen von 13,75 A konnen durch eine besondere Packung der Molekiile erklart werden, wobei die Sauerstoffatome in den Faltbogen nicht auftreten und benachbarte Ketten gegeneinander um eine halbe Monomereinheit versetzt sind. Hierdurch wird die Zwischenzone der Ruckfaltungen besonders dunn (2–3 A).
TL;DR: In this article, the viscosities of dilute solutions of polyisobutylene were measured as function of concentration and rate of shear (0-2500 sec−1).
TL;DR: In this paper, the inhibition effect of 5,6-dichloro-3-vinyl-4,7-dihydro-1H-4-7-indazoledione (1a) on the thermally initiated polymerization of styrene was investigated.
Abstract: Es wurde der Inhibierungseffekt von 5,6-Dichlor-3-vinyl-4,7-dihydro-1H-4,7-indazoldion (1a) auf die thermische Styrolpolymerisation, die Homopolymerisation von 1-Acetyl-4,7-diacetoxy-5,6-dichlor-3-vinylindazol (2a) und von 4,7-Diacetoxy-5,6-dichlor-1-vinylindazol (2c) sowie die vernetzende Copolymerisation von 2a mit 4,7-Diacetoxy-5,6-dichlor-1,3-divinylindazol (2b) untersucht. Durch Verseifung und Propansulfonierung der vernetzten Polymeren wurden stabile Redoxharze dargestellt. Ihre Austausch- (1,8–2,2 maq/g) und Redoxkapazitat (2,5–4,0 maq/g) sowie ihre Mittelpunktspotentiale (467–475 mV bei pH 1,66) wurden ermittelt.
The inhibition effect of 5,6-dichloro-3-vinyl-4,7-dihydro-1H-4,7-indazoledione (1a) on the thermally initiated polymerization of styrene was investigated. In addition the homopolymerization of 1-acetyl-4,7-diacetoxy-5,6-dichloro-3-vinylindazole (2a) and of 4,7-diacetoxy-5,6-dichloro-1-vinylindazole (2c) as well as the copolymerization of 2a with the crosslinking agent 4,7-diacetoxy-5,6-dichloro-1,3-divinylindazole (2b) were studied. After hydrolysis and sulfalkylation of the crosslinked polymers with propane sulfone, stable redox resins were obtained. Their ion-exchange (1,8–2,2 meq/g) and redox capacities (2,5–4,0 meq/g) as well as their midpoint potentials (467–475 mV at pH 1,66) were determined.
TL;DR: In this paper, an optical method for continuously following slow corrosion processes is presented, based on the variation of the optical transmittance and can be applied to very thin (some 1000 A ) metal layers.
Abstract: Die hier verwendete Methode beruht auf der Veranderung der optischen Durchlassigkeit und kann infolgedessen nur auf sehr dunne (einige 1000) Metallschichten angewendet werden. Aufgrund der hohen Werte der Absorptionskoeffizinten von Metallen ist es moglich, mit dieser Methode Auflosungsvorgange in der Grosenordnung monomolekularer Schichten zu verfolgen. Als Lichtquelle wird ein He-Ne-Laser verwendet. Beschrieben werden die folgenden Anwendungen: Auflosungsgeschwindigkeit von Chrom im Bereich der Transpassivitat;Auflosung von Gold in Schwefelsaure mit HCL Zusatz;photolytische Korrosion von Titan.
An optical method for continuously following slow corrosion processes
The method presented here is based on the variation of the optical transmittance and, consequently, can be applied to very thin (some 1000 A ) metal layers only. Because of the high absorption coefficients of metals it is possible by this method to follow dissolution processes of the order of monoatomic layers. The light source used is a He-Ne-laser. The following applications are described: dissolution rate of chromium in the transpassive range; dissolution of gold in sulfuric acid with additions of hydro chloric acid; photolytic corrosion of titanium.
TL;DR: In this paper, the authors show that the intensity of both reflections changes periodically with the thickness of the plate, in such a way, that a maximum in one direction is coupled to a minimum in the other.
Abstract: Bekanntlich sagt die Dynamische Theorie der Rontgenstrahlbeugung voraus, das sich die Verteilung der elektromagnetischen Strahlung in einem perfekten Kristallgitter auf die Wellen in Einfalls- und Beugungsrichtung periodisch mit dem Abstand von der Kristalloberflache andert („Pendellosung”). Es wird gezeigt, das diese sich andernde Aufteilung jedoch im Braggfall anders ist als im Lauefall. Trotzdem ist der im Ausenraum beobachtete Effekt derselbe; die Intensitat schwankt in beiden Fallen periodisch mit der Plattendicke, und zwar so, das ein Maximum in der einen Richtung zu einem Minimum in der anderen gehort.
As is well known the dynamical theory of X-ray diffraction predicts the distribution of the electromagnetic radiation inside a perfect crystal lattice to change periodically among the waves in the direction of incidence and diffraction, depending on the distance from the entrance surface of the crystal (“Pendellosung”). This changing distribution, however, is shown to be different in the Bragg case to that of the Laue case. Nevertheless the effect observed outside the crystal is the same in both cases; that is: the intensity of both reflections changes periodically with the thickness of the plate, in such a way, that a maximum in one direction is coupled to a minimum in the other.
01 Jan 1974
TL;DR: In this article, excited photoelectron spectra were measured on clean polar (111)- and (\( \overline 1/1/1)/1/2 ) faces of GaP and GaAs.
Abstract: He I — excited photoelectron spectra were measured on clean polar (111)- and (\( \overline 1 \overline 1 \overline 1 \))-faces of GaP and GaAs. In general the spectra agree with XPS-and other UPS-data, but in the uppermost valence bands the spectra have stronger structures and differ on both polar faces.