Boron trifluoride: The analysis of 2v3 and the determination of ζ33

1968 ◽  
Vol 46 (8) ◽  
pp. 977-985 ◽  
Author(s):  
Chris W. Brown ◽  
John Overend
Keyword(s):  
High Resolution ◽  
Bond Length ◽  
Boron Trifluoride ◽  
Force Constants ◽  
Experimental Values

The 2v3 bands of 10BF3 and 11BF3 have been studied at high resolution. The experimental values of the Coriolis coefficient ζ33 are 0.7808 ± 0.0036 for 10BF3 and 0.7438 ± 0.0047 for 11BF3. The BF bond length is found to be 1.3102 ± 0.0012 Å. The Coriolis coefficients have been used to fix the E′ species symmetry force constants.

scholarly journals Determination of Residual Stresses in WCu Gradient Materials

1999 ◽  
Vol 33 (1-4) ◽  
pp. 207-217 ◽  
Author(s):  
G. Bokuchava ◽  
N. Shamsutdinov ◽  
J. Schreiber ◽  
M. Stalder
Keyword(s):  
Residual Stress ◽  
High Resolution ◽  
Elastic Behaviour ◽  
Gradient Materials ◽  
Linear Elastic ◽  
Step Functions ◽  
Order Of Magnitude ◽  
Copper Phase ◽  
Experimental Values

Residual stress measurements were carried out on copper–tungsten gradient materials by means of neutron diffraction on the High Resolution Fourier Diffractometer on IBR-2, JINR, Dubna. The samples so far investigated had a concentration profile that approximates the gradient by step functions. The results show an averaged positive stress (stretch) in the copper phase and negative (compression) in the tungsten phase. A comparison to analytical linear elastic calculations shows that the measured values are nearly an order of magnitude too low, whereas however, a qualitative agreement of the stress distribution exists. That this quantitative discrepancy can be attributed to the model's simplifying assumption of pure elastic behaviour can be shown by recent calculations that also include plasticity and show a much better agreement with the experimental values. Single peak evaluation also strongly suggests that plasticity does indeed play a significant role.

High-resolution Raman spectroscopy of gases and the determination of molecular bond lengths

2000 ◽  
Vol 78 (5-6) ◽  
pp. 327-390 ◽  
Author(s):  
W J Jones
Keyword(s):  
Raman Spectroscopy ◽  
High Resolution ◽  
Bond Length ◽  
Subsequent Development ◽  
Bond Lengths ◽  
Pure Rotation ◽  
Wide Range ◽  
Laser Sources ◽  
Vibration Rotation

This review highlights the developments that have taken place in the field of high-resolution Raman spectroscopy of gases from the pioneering studies of Stoicheff and Welsh in the early fifties to the present day. This period has seen major changes in the methods that have been employed for investigating pure rotation and vibration-rotation spectra from these initial studies with Hg excitation through to the deployment of laser sources for incoherent Raman scattering at enhanced sensitivity, and the subsequent development of the techniques of nonlinear Raman spectroscopy at resolutions of ~10-3 cm-1. A central theme in this review is the measurement of accurate rotational constants for nonpolar molecules that have then been employed for the determination of molecular geometries and bond lengths. The studies by Stoicheff of the pure rotational spectra of a wide range of linear and symmetric-top molecules provided an extensive data base that served to supplement bond-length determinations from other methods and enabled him to correlate CC and CH bond length variations in noncyclic compounds with changes in their environment. The discovery of laser sources in the sixties provided exciting new opportunities for the examination of pure rotation and vibration-rotation spectra at enhanced resolution and sensitivity and broadened dramatically the scope of the field. Apart from the improvements in the incoherent scattering methods afforded by these new sources, the discovery of a range of new nonlinear Raman phenomena, a field in which Stoicheff made equally important contributions, led to the creation of a range of new coherent nonlinear Raman methods that have been widely employed for the study of all rotor classes. Representative examples of the many investigations performed with the various spectroscopic methods over this period are given, together with the results of the structure determinations achieved from the analyses of the rotational spectra.PACS Nos.: 33.20Fb, 36.20.Hb

High-resolution microscopy of twin boundaries in gold

1987 ◽  
Vol 45 ◽  
pp. 260-261
Author(s):  
William Krakow ◽  
David A. Smith
Keyword(s):  
High Resolution ◽  
Specimen Preparation ◽  
Gold Films ◽  
Boundary Area ◽  
Transmission Electron ◽  
Recent Developments ◽  
Tilt Boundaries ◽  
High Resolution Microscopy ◽  
Twist Boundaries

Recent developments in specimen preparation, imaging and image analysis together permit the experimental determination of the atomic structure of certain, simple grain boundaries in metals such as gold. Single crystal, ∼125Å thick, (110) oriented gold films are vapor deposited onto ∼3000Å of epitaxial silver on (110) oriented cut and polished rock salt substrates. Bicrystal gold films are then made by first removing the silver coated substrate and placing in contact two suitably misoriented pieces of the gold film on a gold grid. Controlled heating in a hot stage first produces twist boundaries which then migrate, so reducing the grain boundary area, to give mixed boundaries and finally tilt boundaries perpendicular to the foil. These specimens are well suited to investigation by high resolution transmission electron microscopy.

High-Resolution Image Simulation of a Tilted Crystal

1990 ◽  
Vol 48 (1) ◽  
pp. 68-69
Author(s):  
C. J. D. Hetherington
Keyword(s):  
High Resolution ◽  
Crystal Thickness ◽  
Thin Specimen ◽  
Atomic Structures ◽  
Kikuchi Lines ◽  
High Resolution Images ◽  
Final Estimate ◽  
Simulated Images ◽  
Habit Planes

Most high resolution images are not directly interpretable but must be compared with simulations based on model atomic structures and appropriate imaging conditions. Typically, the only parameters that are adjusted, in addition to the structure models, are crystal thickness and microscope defocus. Small tilts of the crystal away from the exact zone axis have only rarely been considered. It is shown here that, in the analysis of an image of a silicon twin intersection, the crystal tilt could be accurately estimated and satisfactorily included in the simulations.The micrograph shown in figure 1 was taken as part of an HREM study of indentation-induced hexagonal silicon. In this instance, the intersection of two twins on different habit planes has driven the silicon into hexagonal stacking. However, in order to confirm this observation, and in order to investigate other defects in the region, it has been necessary to simulate the image taking into account the very apparent crystal tilt. The inability to orientate the specimen at the exact [110] zone was influenced by i) the buckling of the specimen caused by strains at twin intersections, ii) the absence of Kikuchi lines or a clearly visible Laue circle in the diffraction pattern of the thin specimen and iii) the avoidance of radiation damage (which had marked effects on images taken a few minutes later following attempts to realign the crystal.) The direction of the crystal tilt was estimated by observing which of the {111} planes remained close to edge-on to the beam and hence strongly imaged. Further refinement of the direction and magnitude of the tilt was done by comparing simulated images to experimental images in a through-focal series. The presence of three different orientations of the silicon lattice aided the unambiguous determination of the tilt. The final estimate of a 0.8° tilt in the 200Å thick specimen gives atomic columns a projected width of about 3Å.

Determination of the Activity of Pulmonary Tuberculosis: the Utility of High-Resolution Computed Tomography

2000 ◽  
Vol 42 (5) ◽  
pp. 757
Author(s):  
Myung Hee Chung ◽  
Hae Giu Lee ◽  
Won Jong Yu ◽  
Hong Jun Chung ◽  
Bo Sung Yang ◽  
...  
Keyword(s):  
Computed Tomography ◽  
High Resolution ◽  
Pulmonary Tuberculosis ◽  
High Resolution Computed Tomography
Sign in / Sign up

Export Citation Format

Share Document