Presence Of Krypton Research Articles

Ice crystal growth under the presence of krypton and methane at low temperature

To investigate the influence of foreign gas inclusion on the crystallization of ice, we studied the low-temperature (74 < T < 160 K) vacuum deposition of water molecules mixed with Kr or CH4 in a wide range of H2O/gas mixing ratios (0.004 < R < 4) by means of in-situ X-ray diffraction. When H2O vapor containing either Kr or CH4 was condensed onto a cold substrate, ice Ih crystals were found to grow below 130 K in a film of amorphous solid water (ASW), whereas pure H2O gas formed only ASW below 135 K. Small to moderate concentrations (R > 0.2) of Kr and CH4 enhance the formation of ice Ih and increase the crystal size, while at high foreign gas contents (R ⩽ 0.2) that may develop Kr or CH4 crystals below 92 K, the crystal size and relative amount of ice decrease strongly. The maximum ice Ih crystal size in the order of 200 nm was observed with either Kr or CH4 at 92 K for R = 0.2. We propose that Kr and CH4 induce the crystallization of ice by acting as a surfactant.

Effects of krypton on CrSi2 formation

The influence and redistribution of the inert gas Kr in chromium silicide formation have been investigated by MeV He backscattering spectrometry and transmission electron microscopy. It was found that krypton implanted in the chromium film remains stationary with respect to the chromium during silicide formation, but krypton implanted in the silicon substrate accumulate at the silicon/silicide interface. The effect of krypton on the rate of silicide formation is much more pronounced when the krypton is in the chromium rather than in the silicon substrate. The thermal growth of CrSi2 is linear with time in a krypton-free sample, but becomes parabolic when the krypton is incorporated in the silicide at a concentration of 1 at. %. The activation energy associated with Si diffusion through CrSi2 is increased from 1.4±0.1 eV to 2.6±0.1 eV by the presence of krypton in the silicide. The results are interpreted as being due to segregation of krypton on grain boundaries in CrSi2 and subsequent retardation of diffusion along the boundaries.

ChemInform Abstract: Γ‐RADIOSENSITIZED ISOMERIZATION OF GASEOUS BUTENES AND METHYLBUTENES

We have studied the isomerization of butenes and methylbutenes by noble gas-sensitized radiolysis. The isomerization of isobutene to but-2-ene is more efficient in the presence of xenon than in the presence of krypton or argon. The isomerization of but-1-ene into isobutene has a low radiolytic yield and occurs only in the presence of small quantities of dimethylamine. These observations are in agreement with the isomerization of the excited parent ion.In the methylbutene systems, whatever the sensitizing agent, isomerization occurs with a high radiolytic yield. Thus, a chain mechanism is needed to explain the results. The addition of dimethylamine has a reverse effect relative to that observed in but-1-ene. It is concluded that the mechanism invoked for the butene systems is not adequate for explaining the isomerization observed in the methylbutene systems.

Collision Broadening of Principal Series Lines of Barium in the Presence of Krypton

Total absorption method has been applied to 4 s 2 1 S 0 –4 s n p 1 P 1 (6≤ n ≤10) and to 4 s 2 1 S 0 –3 d 4 p 1 P 1 in calcium in the presence of krypton. The determined rate coefficient for Kr-induced broadening increases from 11 to 59×10 -9 cm 3 s -1 as n increases from 6 to 9. This result is reproduced well by a calculation based on a classical broadening theory in which the collision interaction is assumed to be a superposition of the polarization potential and the Fermi potential.

γ-Radiosensitized isomerization of gaseous butenes and methylbutenes

We have studied the isomerization of butenes and methylbutenes by noble gas-sensitized radiolysis. The isomerization of isobutene to but-2-ene is more efficient in the presence of xenon than in the presence of krypton or argon. The isomerization of but-1-ene into isobutene has a low radiolytic yield and occurs only in the presence of small quantities of dimethylamine. These observations are in agreement with the isomerization of the excited parent ion.In the methylbutene systems, whatever the sensitizing agent, isomerization occurs with a high radiolytic yield. Thus, a chain mechanism is needed to explain the results. The addition of dimethylamine has a reverse effect relative to that observed in but-1-ene. It is concluded that the mechanism invoked for the butene systems is not adequate for explaining the isomerization observed in the methylbutene systems.

Some remarks on the interpretation of satellites of the mercury 2537 Å line in the presence of noble gases

New measurements of satellites of the mercury 2537 Å line in the presence of krypton are reported. A high resolution spectrophotometer with a double-channel detecting system was used. The results obtained show that the structure appearing in the wings of the perturbed line arises from two effects: pressure induced satellite bands of HgKr van der Waals complexes and vibrational spectrum of the Hg 2 dimer. The contribution of the latter is demonstrated experimentally by a careful study of the spectrum of pure mercury vapour. It has been shown that this effect is responsible for the series of sharp red bands observed previously in fluorescence by some authors and interpreted there as a result of transitions between bond and free vibrational states in Hgnoble gas systems.

Mechanism of the kryptonation of nickel by film evaporation

Nickel films have been evaporated in the presence of krypton on to a Pyrex substrate maintained at 77 K, and the variation of the krypton incorporation with metal deposition rate and krypton pressure has been studied. Deposition rates were varied between 13 µg and 4.42 mg min–1 and krypton pressures between 3 × 10–3 and 1.3 Torr (0.4 and 173 N m–2). Krypton uptakes of up to almost 6 atom % have been observed. The results are interpreted in terms of a model based on the concept of cryotrapping.

On particular aspects of the competition between stimulated emission and absorption in the 3.36μm xenon line profile

Stimulated emission and absorption have been simultaneously observed in the profile of the 3.36 mu m line of xenon in presence of krypton. Some aspects of the phenomenon can be explained with the simple assumptions of a weak difference of temperature between the two levels.

The influence of krypton on the 2536.52 line of mercury

The 2536.52 ( 1 S 0 - 3 P 1 ) line of mercury has been studied in absorption in the presence of krypton up to a density of 190 Am. Investigations of the shape and the shift of the line have been carried out. Already at very low densities three satellites could be observed at distances of about 34,73 and 128 cm 1 to the violet of the original resonance line. With increase of krypton density the whole pattern shifts to the red. As long as the satellites are clearly distinct the distances between the maxima remain approximately unaltered; at the same time the intensity of the satellites increases. Gradually the pattern changes: first the satellite at 34 cm 1 disappears into the background, then the satellite at 73 cm 1 is over-shadowed by the outer one, and finally, above a density of about 150 Am. the band at 128 cm 1 begins to absorb the original resonance line. The absorption measured in the peak of the outer satellite, as well as that at the violet side increases proportional to the krypton density up to 60 Am; a similar phenomenon was found for the red wing of the principal line, from 100 cm 1 to at least 300 cm 1 from the unperturbed line position, up to 120 Am. The measurements were carried out with unsaturated mercury vapour. Because of the possibility of adsorption of mercury at the steel walls and in view of the qualitative discrepancy between our results for argon concerning the integrated absorption per atom and those of Strijland and Nanassy, the experimental values of the integrated absorption coefficient presented in this paper will not be discussed here.