摘要:

The total energy output of a Ca+laser oscillating on the 866.1‐ and 854.2‐nm emision lines in a double‐pulse laser system as a function of the delay time between pulses has been measured. A very significant increase in the output energy occurs as the delay time between the discharges is decreased, reaching a maximum value at about 90 &mgr;sec for the discharge conditions employed. This improvement in performance is attributed to the difference between the destruction rates of the Ca+ions in the 3d 2D3/2and 3d 2D5/2laser terminal states and that of the 4s 2S1/2Ca+ion ground state and to the fact that the initial discharge produces a considerable concentration of Ca+ions which persist until the second discharge occurs. The consequences of this observation to the construction of a high‐repetition‐rate laser are discussed.

ISSN:0021-8979    

DOI:10.1063/1.325994

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Population transfer in HF by both collisional and radiative processes was measured by ir‐laser double‐resonance experiments. In three kinds of experiments populations pumped to a specific rotational level were followed: out of the pumped level, to the levels above, and to the levels below. The rates of loss from the pumped level and transfer to the lower levels were strongly affected by lasing between rotational levels. Data for gain and laser intensity were incorporated into a kinetic rate model to evaluate transfer rates.

ISSN:0021-8979    

DOI:10.1063/1.326076

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Stable glow discharges have been demonstrated in thallium‐mercury gas mixtures at mercury densities of 3×1019and temperatures of 500–900 °C. These discharges have shown themselves to be highly efficient in producing excited Tl (72S1/2) atoms and Tl‐HgB2J1/2excimer molecules. Discharge efficiency as high as 30±10% in producing Tl (72S1/2) and Tl‐HgB2J1/2points to the possibility of the creation of a Tl‐Hg excimer laser operating at similar efficiencies. These highly efficient discharges are thought to be due to very fast transfer of energy from mercury excimers into Tl‐Hg. The transfer cross section from excited molecular mercury to Tl (72S1/2) and Tl‐Hg excimers is found to be approximately 1.2×10−14cm2.

ISSN:0021-8979    

DOI:10.1063/1.326077

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Chloroapatite (Na2Nd2Pb6(PO4)6Cl2), a Nd3+compound with 3.4×1021ions cm−3has been shown recently to possess a high fluorescence efficiency. Measurements on single‐crystal samples show that the oscillator strengths and the fluorescence quenching are both slightly smaller than in Nd pentaphosphate (NPP). Laser effect with longitudinal Ar* laser excitation is reported for the first time in this material on two lines at 1.0585 and 1.0675 &mgr;m, which have orthogonal polarizations and equal thresholds, in agreement with fluorescence spectra. The laser threshold (absorbed powerforagiventotal cavity loss) isnearlyequal to that of a NPP crystal in the same cavity.

ISSN:0021-8979    

DOI:10.1063/1.326023

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Discharge development processes, such as homogeneous glow formation, glow‐to‐filamentary arc transition, and arc formation, of moderate volume CO2TEA laser medium with external ultraviolet (uv) volume preionization are studied by a high‐speed‐camera technique. The framing records in this paper supplement the earlier streak ones of CO2TEA laser discharges of Sakaietal. The records show that instability appears as a bright spot at the cathode in the middle of the uniform glow stage, then propagates in the anode direction, keeping the shape of a bright spot or changing into a bright filament. This propagation continues even after termination of the volume‐dominated glow. The discharge development is found, from an understanding of the current waveform, to be considerably sensitive to the CO2, N2, and He composition ratio, and the pulse‐forming network and other characteristics are also studied. The glow‐to‐arc transition mechanism and the dominant contributor to suppress arc formation are discussed.

ISSN:0021-8979    

DOI:10.1063/1.326024

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Argon‐laser‐pumped single‐transverse‐mode laser operation was obtained with a three‐dimensionally confined LiNdP4O12slab waveguide laser, in which one endface was cylindrically polished and directly coated with a laser mirror. The threshold, the output power, and the oscillating transverse modes were theoretically analyzed, both for transverse pumping and for longitudinal pumping, considering the spatial distribution of the pump beam and the laser beam. The necessary conditions for the pump sources to obtain a TE00single‐transverse‐mode oscillation were determined on the supposition of the diode pumping.

ISSN:0021-8979    

DOI:10.1063/1.326025

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Acoustic emission in liquid crystals has been experimentally assessed. The emission has been studied as a function of temperature for different mesophases. The effect is attributed to the release of elastic energy involved in the defect dynamics inside the material.

ISSN:0021-8979    

DOI:10.1063/1.326026

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Several articles have been written on the subject of scanning acoustic microscopy. Nevertheless, apart from some specific papers dealing with reflection microscopy, little has been said about the various contrast mechanisms involved in the process of image formation, and the effects of parameters such as acoustic antireflection coatings on the lens surface and absorption in the water on the quality of the recorded image. This paper is devoted to an analysis of these problems. It is shown that in the amplitude mode of operation, the acoustic microscope acts as a phase contrast microscope and is sensitive to the local phase gradients in the object. Furthermore, it is shown that the effect of an acoustic antireflection coating on the lens surface is to substantially reduce the side lobe amplitude of the focal distribution at the expense of a slight increase in the width of the main lobe. Experimental observations agree with theory.

ISSN:0021-8979    

DOI:10.1063/1.326027

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

By introducing suitable parameters, it is demonstrated that the heat conduction effect resembles an elastic deformation. The difference is that the mechanical stress variation induces an inertia effect, while the heat stress variation generates a diffusion effect. Guided by this resemblance, a compatible Lagrangian formulation and its complementary form are derived for the heat conduction problems. The results are similar to Biot’s variational principles. The advantages of using the complementary form for the approximate solutions are also discussed. Temperature distributions in a semi‐infinite solid with prescribed wall temperatures and with described heat flux are considered as illustrative examples.

ISSN:0021-8979    

DOI:10.1063/1.326028

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A steady two‐dimensional MHD boundary‐layer flow on a flat plate with varying hydrostatic pressure and free‐stream velocity along the plate and a uniform transpiration through the plate is considered. The momentum boundary‐layer thickness is found to increase substantially with injection and negative flow‐shape factors. However, it decreases with increasing magnetic interaction numbers. Transpiration, flow‐shape factor, as well as magnetic interaction number strongly affect the shearing stress at the wall. Injection and retarding free‐stream velocity will enhance the chances of a flow separation, while the magnetic interation number will do just the opposite.

ISSN:0021-8979    

DOI:10.1063/1.326029

出版商:AIP    

年代:1979

数据来源: AIP