High-resolution spectra of the infrared-active stretching fundamental ν3 of 238UF6 have been obtained between 620.6 and 633.5 cm−1 using tunable semiconductor diode lasers. Interference from hot bands was suppressed by cooling the UF6 in a supersonic expansion, and useful monomer concentrations were produced with effective temperatures of <100 K. Portions of the band from P(77) to R(66) are illustrated. All transitions from the vibrational ground state have been assigned, and the Q branch has been fully analyzed. A total of 43 line frequencies and 110 frequency differences extending in J to P(77), Q(91), and R(67) has been used to fit seven spectroscopic constants. The ground- and excited-state values of the rotational constant B could be individually determined, and the U–F bond length in the ground vibrational state is r0=1.9962±0.0007 Å. The Q branch of 235UF6 has also been analyzed and the 235UF6–238UF6 ν3 isotope shift measured to be 0.603 79±0.000 17 cm−1. The isotope shift and the Coriolis constant ζ3 have been used to refine the general quadratic intramolecular force field of UF6, and the Cartesian displacement coordinates of both infrared-active fundamentals are illustrated and compared with those of SF6.
The field emission microscope has been applied to a study of the allotropic transformation in single microcrystals of titanium. Patterns with symmetry characteristic of the high and low temperature phases are presented. Techniques for analyzing the patterns are outlined. Data derived from the pattern analyses give an orientation relation between patterns of the two phases that is consistent with the Burgers relation. The field emission microscope thus constitutes a new method for direct observation of phase changes. At the same time, it offers to the study of allotropic transformations the advantages of high resolution and great magnification that are not available with conventional methods.
Periodic deviations in the Schottky effect for molybdenum have been measured over a field range of 10 4 to 10 5 volts cm -1 in a temperature range of 1400 to 1800°K. The results, interpreted in terms of the two reflection parameters X and jx, justify the assumption of a mirror image barrier for the emitted electrons.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.