Hans Pettersson

Long-range Particles from Radium-active Deposit

WHILE studying the H-particles found by Sir Ernest Rutherford to be the first disintegration product of aluminium and some other atoms, under α-bombardment, we have developed a new method for obtaining strong and practically constant sources of such radiation. The method consists in enclosing dry radium emanation mixed with pure oxygen within thin-walled capillaries of hard (potassium) glass, lined with some 12 µ thickness of aluminium foil pressing well against the glass. As a small number of long-range particles were given off from the glass itself, we have also made use of capillaries drawn out from tubes of pure silica.

Die Zerlegung der Elemente durch Atomzertrümmerung

ZusammenfassungDie noch bestehenden Abweichungen zwischen den Ergebnissen in Wien und in Cambridge auf dem Gebiete der Atomzertrümmerung werden besprochen. Zur Erklärung werden die Unterschiede in der verwendeten Methodik herangezogen und ein Übersehen der schwachen Szintillationen der langsamen H-Teilchen als Grund für die negativen Resultate der Cambridger Versuche angegeben. Durch Versuche nach unabhängigen Methoden wird diese Erklärung gestützt und die früheren Angaben der Wiener Arbeiter über die Zertrümmerung verschiedener Elemente aufrechterhalten.

Measurements of Submarine Daylight

IN the course of the last nine years Poole and Atkins1 have developed a very ingenious method for measuring the intensity of the daylight penetrating into the sea by means of alkali-metal photo-cells, using a delicate balance method for measuring the very weak photo-currents. The many vagaries of the photo-cells make measurements with this contrivance rather difficult to any but trained experimenters. In order to find a simpler and less expensive method of measuring submarine daylight we have used the novel ‘Sperrschicht’ selenite photo-cells due to Dr. B. Lange. As these cells give a photo-current several hundred times more intense than the most sensitive of the alkali cells, it is possible to use an ordinary pointer galvanometer, or some similar instrument, for the observations, while at the same time they are simpler and more easily manipulated by relatively untrained observers. The instrument used for our measurements gave a deflection of one scale-unit for 3.76 × 10−7 amperes and could be read to within 0.1 scale-unit. Another advantage of the Lange cell is its broad maximum of sensibility between 4500 and 5500 A., that is, with its centre near the minimum of light-extinction found by Knudsen for coastal water at 5100 A. The narrow region of maximum sensibility characteristic of the potassium cell is situated much nearer the violet end of the spectrum.

Luminous Discharge in Gases at Low Pressures

CONSIDERING the very minute quantities of matter required for a luminous discharge in gases at low pressures excited by electric oscillations of high frequency, this method would seem to be specially adapted for spectroscopic tests for the products from atomic disintegration, spontaneous as well as artificial. Experiments to this end were started some time ago in the Institut für Radiumforschung of Vienna and have recently been carried further in this Institute. The following phenomena, which appear to be of general interest, were observed.

Die Zertrümmerung des Kohlenstoffatomes

ZusammenfassungVersuche nach der Szintillationsmethode werden beschrieben, welche die vom Verfasser vor drei Jahren nachgewiesene Zertrümmerbarkeit von Kohlenstoff in reinster Form bestätigen. Versuche nach unabhängigen Methoden, photographische und Wilsonmethoden, welche zu demselben Ergebnis geführt haben, werden erwähnt. Einige theoretische Folgerungen betreffs des Aufbaues der Kerne von Kohlenstoff und anderen Elementen werden gezogen.

The Ridge in the Indian Ocean between Chagos Is. and Socotra

THE main reason why the name of “Johannes Schmidt Ridge” is preferable to that of “Carlsberg Ridge” appears to me to be that the former name conforms better with the traditions of oceanographical science than the latter. Ridges or depressions of the ocean floor have so far, where a geographical name already existing has not been used, almost exclusively been named, either after the ship from which they were discovered, or after some famous seafarer or investigator. There are, it is true, instances where geographical discoveries have been named after individuals or institutions in recognition of financial support. But in the present case, dealing as we are with one of the main features of the earths crust, the name of its discoverer appears most appropriate, a name which Dr. Schmidts modesty would, needless to say, have precluded him from putting forward himself.

Observations of Water Trajectories in the Open Sea

DIRECT observations of continuous movements of water masses in the open sea do not appear to have been carried out before. We have, for this purpose, for some years been using free drifting current-crosses, followed by our research steamer the Skagerak. The crosses are made from two sheets of corrugated iron, intersecting at right angles, with the line of intersection vertical, and presenting an area to the current of approximately one square metre. They are suspended from a cylindrical buoy of small dimensions drifting at the surface with its axis vertical. The buoy carries a very light rod projecting upwards with a small electric lamp at the top, of the type used by drifters for their nets. By varying the length of the thin wire rope by which the cross is suspended from the buoy, one may study the water movements in different depths, since the small resistance due to the surface buoy does not affect the movements of the cross to any large extent, so long as the current below is not too weak relatively to the surface current. The positions of the buoy are observed at intervals of an hour or less by bringing up the ship as close to the drifting system as possible, without interfering with its movements. In daytime, with moderately strong currents, the movements of the buoy are followed from the ship at anchor by means of a Zeiss tele-meter. Such drifting systems have occasionally been followed right across the Skagerak from Skagen to the lighthouse Måseskär on the Swedish coast.

Die Sichtbarmachung vonH-Strahlen

ZusammenfassungEs werden zwei einfache Anordnungen beschrieben, um nach der Wilson schen Methode, bzw. nach der Szintillationsmethode, die „natürlichen“H-Strahlen aus α-bestrahltem Paraffin in größerer Zahl beobachtbar zu machen.

ber die Ausbeute bei Atomzertrmmerungsversuchen

ZusammenfassungDie Faktoren, welche die Ausbeute an Atomtrümmern bestimmen, werden besprochen und die Unterschiede zwischen den neuerdings von Bothe und Fränz mit dem Spitzenzähler gefundenen Werten und den früher in Wien nach verschiedenen Methoden erhaltenen diskutiert. Die von den erwähnten Autoren vorgeschlagene Erklärung, daß bei den Szintillationszählungen in Wien individuelle β-Teilchen beobachtet und für H-Teilchen gehalten wurden, wird als unhaltbar zurückgewiesen. Anstatt dessen werden die Unterschiede, insofern sie nicht auf verschiedenen Versuchsbedingungen beruhen, auf ein Versagen des Spitzenzählers, die H-Teilchen quantitativ zu registrieren, zurückgeführt. Bei den Versuchen von Bothe und Fränz nach der Vorwärtsmethode dürften natürliche H-Teilchen aus Wasserstoffverunreinigungen zu übertriebenen Ausbeutezahlen geführt haben. Die Versuche, retograde Atomtrümmer zu finden, welche nach ihrer Erklärung durchweg negativ verliefen, werden anders gedeutet, und zwar in positivem Sinne. Besonders bei Kohlenstoff bedeuten die Ergebnisse von Bothe und Fränz, richtig auf-gefaßt, eine Bestätigung für die in Wien gefundene Zertrümmerbarkeit dieses Elements, da die einzige sonst übrigbleibende Erklärung, daß eine stark über normale Streuung von α-Teilchen vorliegt, sowohl auf Grund theoretischer Über-legungen wie im Lichte neuer Versuche nicht zulässig ist.

Der Heliumkern als Baustein anderer Atomkerne

ZusammenfassungAuf Grund der neuen Atomgewichtsbestimmungen von Aston werden einige Argumente gegen einen allgemeinen Heliumaufbau der Materie vorgebracht.