Kenneth W. Billman

Collisionless dissociation and isotopic enrichment of SF6 using high-powered CO2 laser radiation

Abstract Dissociation of 32 SF 6 and the resultant isotopic enrichment of 34 SF 6 using high-powered CO 2 laser radiation has been studied with higher experimental sensitivity than previously reported. Enrichment factors have been measured as a function of laser pulse number, wavelength, energy and time duration. A geometry-independent dissociation cross section is introduced and measured values are presented. Threshold energy densities, below which no dissociation was observed, were also determined.

Gain and fluorescence measurements in photoionization-stabilized XeF discharge lasers operating at high-energy loadings

A recently developed simple photopreionization‐stabilized discharge scheme was adapted successfully to the excitation of XeF and KrF lasers at pressures of 0–1500 Torr. The authors report on the stabilization and excitation characteristics of F2 and NF3 : Xe : He discharges over a wide range of energy loadings. These results summarize and compare the detailed fluorescence and gain measurements. The (nonoptimized) XeF output energies of ∼1 J/liter compare favorably with those of other devices.

Measuring the velocity of individual atoms in real time

It is proposed that the thermal velocity of a single atom could be measured in real time using a laser time-of-flight velocimeter (LTV) operating on the principle of laser resonance fluorescence. Theoretical data are presented for several atomic species that have resonances within the range of available dye-laser systems. It is shown that measurements in the subsonic region are certainly feasible. The atoms could be either in vacuum or in a buffer gas, e.g., at atmospheric pressure. Measurements in the transonic and supersonic region also appear possible. One potential application is the measurement of flow speeds in wind tunnels, perhaps as high as Mach 45.

Infrared-pumped third-harmonic and sum-frequency generation in diatomic molecules

Using molecular hydrogen as a model system, we present the first calculation which demonstrates the feasibility of efficient third‐harmonic and sum‐frequency generation of ir laser radiation by diatomic molecular gases. A conversion efficiency of 10% without phase matching is achievable with a modest laser intensity of about 20 MW/cm2. In addition to a two‐photon resonance, the efficient conversion depends on a mechanism which makes use of virtual vibronic transitions exclusively. Possible methods for phase matching are also suggested.

Measurement of density and temperature of a hydrogen plasma using an argon laser

Curves relating the absorption of the argon ion laser lines at 0.488 and 0.515 μm to the electron density and plasma temperature of a hydrogen plasma are presented. A technique for determining these plasma parameters by means of simple absorption measurements is discussed.

Adequacy of classical inverse bremsstrahlung theory for low‐temperature plasmas

Recent improvements in diagnostic and computation techniques have made it possible to conduct sensitive experiments on plasma heating and thermal conductivity. The adequacy of classical absorption theory for low‐temperature (T<20 eV) subcritical density experiments is examined.

Absorption of laser radiation in a H‐He plasma. II. Experimental measurement of the absorption coefficient

The absorption coefficients of 0.633‐, 1.15‐, and 3.39‐μm laser radiation for a homogeneous H‐He plasma have been measured in the temperature range of 12.2 to 21.7 (× 103 °K) and in the electron number density range 0.45 to 6.5 (× 1017 cm−3). Good agreement is found between the experimentally determined total absorption for each of the wavelengths and that calculated from theory. Furthermore, because the 3.39‐μm absorption is dominated by inverse bremsstrahlung while the 0.633‐μm absorption is dominated by photoionization and resonance absorption, the experiment indicates a correct assessment by the theory of these individual absorption mechanisms.

Cautionary Note Concerning the CUSO 4 X-RayLaser

For the so far unconfirmed lasing action claimed by Kepros et al. (1972) to have been obtained by focusing a 1.06-micron radiation of a q-switched Nd(3+) glass laser to a small cylindrical volume inside a CuSO4-doped gelatin medium supported between two glass plates, an alternate explanation is proposed that does not depend on the assumption of laser action in copper. The proposed explanation shows how collimated X-ray beams might be created under the experimental conditions described by Kepros et al.

Photodetector Triggered Pulse Selection from a Mode Locked Ruby Laser

A technique for external selection of a single pulse from the output train of a mode locked ruby laser is presented. Ease of optical alignment and the ability to be triggered by a small individual pulse early in the train are the chief advantages of this photodetector technique over that of spark gap triggering.

Comments on “measurement of the absorption coefficients for the He−Ne laser radiation in a pure hydrogen plasma”

In a recent publication in this journal, Öke described an experiment designed to measure the total absorption coefficients for 0.6328- and 1.15-μm He−Ne laser radiation in a hydrogen plasma. It is the purpose of the present note to indicate some errors in the publication which invalidate the conclusions drawn by the author.