摘要:

A broadband tunable single‐frequency color center laser optothermal molecular beam spectrometer has been constructed.Kcomponents have been resolved forP(18) toR(11) rovibrational transitions in &ngr;1CH3C≡C–H. The observed transition linewidths are demonstrated to be ≤6 MHz and are determined with a relative precision of ≤10 MHz over the 15‐cm−1frequency segment scanned.

ISSN:0034-6748    

DOI:10.1063/1.1139110

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A method is described for stabilization of a cw CO2laser by locking it to a modulated external cavity which is locked to a HeNe reference laser. This avoids the necessity of modulating the CO2laser. Stability values of a few tens of kHz on the microsecond and minute time scales have been achieved.

ISSN:0034-6748    

DOI:10.1063/1.1139121

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An electronic coupled triple monochromator is presented. The system is composed of double and single monochromators coupled together electronically and controlled by a microcomputer. The tracking is obtained via a feedback loop between the motor’s velocities and two shaft encoders which are connected to the lead screws. The resolution of the system was measured as a function of the slits width and the wavelength and is as good as the resolution of a double monochromator. The additional loss in light intensity results only from the reflection loss in the grating and in the mirrors of the third stage.

ISSN:0034-6748    

DOI:10.1063/1.1139128

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A small‐volume long‐path absorption cell has been designed for use with condensable samples. The absorption cell is temperature controlled and operates over the temperature range of −10 to 80 °C. To prevent condensation of the sample on the mirror surfaces, the mirrors are individually temperature controlled and maintained a few degrees above the ambient temperature of the absorption cell. The cell has been tested and used to measure weak absorptions in water vapor in the near infrared.

ISSN:0034-6748    

DOI:10.1063/1.1139136

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A simple technique for photoacoustic spectroscopy at low temperature using a rf‐sputtered ZnO film transducer is described. We succeed in obtaining the spectra of InSe at low temperatures. The signals due to the free exciton annihilation and the nonradiative donor to valence band transition are clarified by the present technique. These results establish the usefulness of low‐temperature photoacoustic spectroscopy for studying transition processes in semiconductors.

ISSN:0034-6748    

DOI:10.1063/1.1139109

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An improved Lyman‐alpha hygrometer has been developed in order to measure high‐frequency small‐scale fluctuations of water vapor concentration in the lower atmosphere and in tunnels (e.g., IMST large air–sea interaction simulation tunnel). The sampling volume is reduced to 3 mm in diameter by aerodynamic shaping; the signal‐to‐noise ratio is largely increased by designing special UV sources and using a photomultiplier connected to a low‐noise electrometer; parasitic sensitivities are reduced by a precise control of the variable path length and by filtering the UV beam with an oxygen cell. This article describes the problems and improvements related to reducing the sampling volume and presents some characteristic spectral functions obtained in IMST tunnel, up to 200 Hz. A further article will describe the O2filtering technique, the control of sensitivity, and the data reduction procedures.

ISSN:0034-6748    

DOI:10.1063/1.1139111

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We show that the absolute determination of the refractive index when combined with an expansion technique for obtaining the higher‐order coefficients of the Lorentz–Lorenz expansion leads to precise values of density. The compressibility factor of methane calculated with the first three coefficients of the Lorentz–Lorenz expansion is comparable to the best PVT values. The optical method for the determination of the compressibility factor is shown to be not only precise, but also has the ability to produce numerous experimental points in a short time as compared to other methods.

ISSN:0034-6748    

DOI:10.1063/1.1139112

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Laser diffraction produced by a single layer of erythrocytes in suspension is applied to assess the cell deformation in the erythrodeformeter. It is well known that erythrocytes become elliptically deformed when a fluid shear stress is applied to them. In the erythrodeformeter the red cell suspension fills the narrow gap between two parallel disks of glass, horizontally positioned, the lower of which rotates at a controlled speed while the upper is fixedly supported. A laser beam traversing the sample layer atrdistance from the center of disks, displays a diffraction pattern ‘‘at infinity.’’ At no shear stress the cells have discoidal shapes and the diffraction pattern is circular. Shear‐induced elongation of cells leads to an elliptical diffraction pattern, its geometric characteristics being directly related to those of deformed cells. This deformation can be evaluated in terms of a deformation index calculated from the width and the length of the diffraction pattern ellipse. In the erythrodeformeter a similar index is evaluated from the light intensity traversing two slots of uniform width each one coincident with each of the two principal diameters of the pattern ellipse, the light intensity being measured by a photoelectric detection head.

ISSN:0034-6748    

DOI:10.1063/1.1139113

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A simple device is described to test the circular polarization of microwave radiation. It employs two matched apertures, opposite 45° twists, and a hybrid coupler to separate and measure the two circularly polarized components of an incident wave.

ISSN:0034-6748    

DOI:10.1063/1.1139114

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new type of instrument has been designed and built to make Fourier transform nuclear‐magnetic‐resonance (NMR) spectroscopic measurements at temperatures to at least 1200 °C, with a resolution of about 1 ppm. A sample is rapidly and repeatedly shuttled between the furnace and the radio frequency (rf) coil of the NMR probe (both located within a high field superconducting magnet), spending most of the time in the furnace. During each cycle, a series of rf pulses may be given and a single free‐induction decay sampled. The rf coil is located outside of the furnace and is maintained at room temperature despite its close proximity to the sample. Electronic stability and coil ‘‘filling factor’’ are thus both optimized. The sample temperature drops below that of the furnace when cycling begins, but rapidly approaches a nearly constant value with only small fluctuations. 99% BN has been successfully used as a sample container in experiments on27Al,29Si, and23Na in molten silicates in the system Na2O–Al2O3–SiO2.

ISSN:0034-6748    

DOI:10.1063/1.1139115

出版商:AIP    

年代:1986

数据来源: AIP