George C. Baldwin

Microholography of living organisms.

By using intense pulsed coherent x-ray sources that are currently under development, it will be possible to obtain magnified three-dimensional images of elementary biological structures in the living state at precisely defined instants. For optimum contrast, sensitivity, and resolution, the hologram should be made with x-rays tuned to a resonance of nitrogen near 0.3 nanometer. Resolution will then be limited mainly by the hydrodynamic expansion that occurs while the necessary number of photons is being registered. Problems of technique are also briefly discussed.

Gamma-ray lasers?

Abstract This paper reviews the essential requirements for observing stimulated emission of recoilles gamma radiation, categorizes and discusses the difficulties attending various proposals for creating an ultrashort-wave radiation source based on the Mossbauer effect.

Kinetics of nuclear super‐radiance

We derive the minimum requirements for super‐radiant gamma‐ray emission by applying the semiclassical theory of coherent spontaneous emission to the case of nuclear transitions in a crystal host. We find that, if a pure sample of a storage isomer can be rapidly transferred into an inverted population for a recoilless transition, less than 1013 nuclei should suffice for an experimental demonstration of nuclear super‐radiance.

Nuclear excitation by laser driven coherent outer shell electron oscillations

It is emphasized that laser driven coherent multielectron oscillations of the outer electron shell will offer a suitable pumping mechanism to achieve nuclear excitation for probable lasing in the gamma radiation range. 235U is discussed for such a possible excitation.

A critical review of gamma‐ray laser proposals*

Laser sources generating sub‐nm radiation, using recoilless nuclear transitions in solids, have been proposed for years. This review examines, from the standpoint of kinetics, many solutions (viz., narrowed line, explosive neutron pump, two‐stage pump, two‐step pump) that have been proposed for the basic problem: that pumping can inhibit or destroy the Mossbauer and Borrmann effects, which are essential for gain.

Kinetics of nuclear superradiance

The feasibility of achieving laser action in the gamma radiation range is discussed. The possible mechanisms pumping, and the rapid transfer of active nuclei into the upper laser level are discussed. An analysis of kinetics of superradiant nuclear gamma‐ray emission is given.

Assessment of a method proposed for finding transfer levels for isomeric deexcitations

The existence of closely spaced nuclear levels with disparate lifetimes is an essential feature of recent proposals for gamma‐ray lasers. Resolving such pairs of levels is beyond the present capabilities of nuclear spectroscopy. In this work, we consider the possibility that exposure of an isomer to a continuum of radiation, specifically a pulse of black body radiation produced by a laser, would reveal the second level. We compare the required couplings of the nucleus to the photon field with those observed. We conclude that this method probably is not appropriate for finding transfer levels.

Predicted changes of the internal conversion rates in 119Sn due to admixtures of lower multipole order

One conceivable basis for interlevel transfer from a long‐lived isomer to graser state might be to alter the multipolarity of the transfer step. As an example, in the case of 119Sn any mechanism that introduces angular momentum to admix M3 radiation into the normally M4 transition from the 89.6 keV, 11/2− level to the 23.9 keV 3/2+ state could greatly shorten its normal 293 day halflife. We have calculated the K‐shell internal conversion rate for the 89.6 keV level in 119Sn for small admixtures of M3 radiation using Moszkowski formulas for the radiative transition rates and tabulated values of the internal conversion coefficients. We find that even very small admixtures of lower multipole order can produce very large changes in the internal conversion coefficient. This offers the basis for a simple and definitive test of the hypothesized mechanism for creating population inversion by introducing angular momentum.

Multistep Pumping Schemes for Short-Wave Lasers

The development of sources that can generate coherent radiation at wavelengths much shorter than conventional lasers is an important goal of current research in many institutions. At Los Alamos, studies of the feasibility of gamma-ray lasers have been under way for several, years, and a new approach to making an X-ray laser has been recently conceived. We are seeking ways to reduce the pumping power requirements.