Images of gas molecules by electron holography. I. Theory

It is demonstrated that molecular images with an Abbe resolution limit as fine as 0.1 Å can, in principle, be reconstructed optically directly from appropriately recorded electron diffraction plates (holograms). Even when a sample of randomly oriented gas‐phase molecules is chosen as a subject, reconstructed images with a well‐defined physical interpretation can be made. If the molecules are selected to contain just one heavy atom—this atom to generate a strong ’’reference wave,’’ by scattering, so as to satisfy Gabor’s conditions for the production of a hologram—the reconstructed images correspond to rotational averages about the heavy atom. If no single atom dominates, the ’’image’’ is not as simple conceptually but the reconstruction is shown to display a series of rings, each of which corresponds to an interatomic distance in the molecule. The physical basis of the approach is reviewed, followed by a mathematical treatment of the electron scattered intensity and optical reconstruction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70561/2/JCPSA6-70-8-3952-1.pd

Evaluation of Two Systems Used to Extract Alfalfa Weevil Larvae (Coleoptera: Curculionidae) from Alfalfa Samples

A modified Berlese funnel system was developed to extract alfalfa weevil larvae (Hypera postica) from quadrats 30.5 cm on a side. Data from this system were comp.wed with simultaneous data from a hand sorting extraction system. In most instances, the modified Berlese system was as efficient as the hand sorting method and the number of man hours required to process samples by hand was far greater than that required by the Berlese system

Electron Diffraction Study of Monomethyl‐ and Dimethylphosphine

The structural parameters of gaseous monomethyl‐ and dimethylphosphine were determined by the sector‐microphotometer method of electron diffraction. Center of gravity bond distances and standard errors for the two molecules were, respectively: rCP=1.858±0.003 A and 1.853±0.003 A; rCH=1.094±0.008 A and 1.097±0.007 A; rPH=1.423±0.007 A and 1.445±0.02 A. The angles P☒C☒H were 109.6±1° and 109.8±0.7°. In dimethylphosphine the angle C☒P☒C was 99.2±0.6°. The methyl groups were found to be in staggered conformations. The distances and root‐mean‐square amplitudes of vibration agreed well with the values determined in recent studies of phosphine and trimethylphosphine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70459/2/JCPSA6-32-3-832-1.pd

Bond lengths of vibrationally hot AXn molecules. A simple treatment

Given the form of an anharmonic, modified Urey–Bradley molecular force field for AXn molecules, it is shown how to express the mean vibrational displacements of bond lengths from equilibrium lengths re simply in terms of elementary quantities. The dominant terms isolated are due to Morse stretching anharmonicity, nonbonded interactions, and the centrifugal stretching of bonds encountered as the atoms swing over arced trajectories in bending vibrations. Illustrative calculations are presented for CH4 and CD4.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70616/2/JCPSA6-70-10-4581-1.pd

Modification of Glauber theory for dynamic scattering of electrons by polyatomic molecules

In its original form, Glauber scattering theory achieves a considerable simplification by neglecting several factors of modest consequence in atomic scattering but of importance in molecular scattering. These include, in particular, the spread of the shadow cast by a scatterer as a wave propagates downstream in the target. Although such effects do not matter in the original range of validity of the theory, the characteristic distances in molecules restrict the unmodified theory to an excessively small angular range. The present treatment introduces phase factors to take into account the distribution of scatterers in the incident direction and the propagation of the scattered waves in the target. This appreciably extends the formal range of applicability.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69897/2/JCPSA6-63-9-3750-1.pd

Evidence for Pseudo‐Jahn—Teller Effect in XeF6

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70654/2/JCPSA6-46-11-4530-1.pd

Disease as a Larval Mortality Factor in Alfalfa Weevil, \u3ci\u3eHypera Postica\u3c/i\u3e (Coleoptera: Curculionidae) Populations in Illinois

During the 1974 growing season, larvae of the alfalfa weevil, Hypera postica (Gyllenhal), were examined for pathogens. Three larvae out of 715 examined were infected with a microsporidium. This infection was present in both Washington and Mason counties in Illinois

Representations of molecular force fields. IV. Vibrational stress, isotope effects, and structure of ethane

The transformation of molecular force fields from natural curvilinear coordinates S to rectilinear coordinates S (yielding simpler equations of motion) is discussed. Rectilinear cubic constants include mass dependent terms arising from the nonlinear coordinate transformation as well as contributions from the cubic constants for the S displacements. These contributors to anharmonicity lead to intramolecular ’’vibrational stresses’’ resolvable into components FC, FT, and FF which induce rectilinear molecular strain components 〈S〉C, 〈S〉T, and 〈S〉F, each of which has its own physical interpretation. More significant than the rectilinear quantities are the curvilinear stresses and strains which, it is shown, are readily expressed in terms of the above components. Each of the foregoing quantities is easily decomposed into contributions from the various types of vibration. Magnitudes are illustrated by computations of cubic force constants and selected stress and strain components in C2H6 and C2D6.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70860/2/JCPSA6-67-9-4168-1.pd