摘要:

A detailed description is given of a liquid‐helium‐cooled. Fourier transform spectrometer recently flown on a rocket. The instrument was used to make new precise measurements of the spectrum of the cosmic background radiation in the wave number range 2–30 cm−1, as reported by H. P. Gush, M. Halpern, and E. Wishnow [Phys. Rev. Lett.65, 537 (1990)].

ISSN:0034-6748    

DOI:10.1063/1.1142534

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The development of a new time‐resolved Fourier transform spectrometer that is capable of 0.25 cm−1spectral resolution and better than 10−7s temporal resolution in the visible is reported. The time‐resolved capability of the spectrometer is achieved by coupling a step‐scan interferometer to a transient digitizer/laser system. The operation of the spectrometer is described in detail, and scattered light and laser‐induced fluorescence spectra from an I2gas cell are presented to demonstrate the temporal and spectral resolution of the spectrometer.

ISSN:0034-6748    

DOI:10.1063/1.1143815

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In this article we present as an experiment in single‐photon‐decay spectroscopy an alternative method to that based on the measurement of the probability distribution function,Pf(t), of the time intervals for the time of arrival of the first photon after the excitation pulse. We propose the measurement of the sine transform ofPf(t), which gives a maximum when the fluorescence signal is of the single exponential decay type. The existence of this maximum allows us to determine very accurately the value of the decay constant using a number of measurements which is lower than that required to establish aPf(t) that is accurate enough to draw the same conclusions. A theoretical model of the error is studied and is compared by means of a computer simulation with the usual method of measuringPf(t). An experiment is performed using a TMMC crystal to verify the validity of the theoretical predictions and of the simulation results.

ISSN:0034-6748    

DOI:10.1063/1.1142535

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have demonstrated the performance of a position‐sensitive and time‐resolved photon counting system based on a microchannel plate photodetector with a delay‐line anode, in combination with a picosecond laser source and two‐channel fast timing technique. A spatial resolution of 220 &mgr;m and a temporal resolution of 500 ps were achieved. Examples of two‐dimensional, both spectrally and temporally resolved molecular emission spectra are presented. The results obtained clearly show the method to be suitable for those spectroscopic applications that require an extremely high sensitivity and multichannel spectral analysis with picosecond time resolution.

ISSN:0034-6748    

DOI:10.1063/1.1142536

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A highly sensitive, spontaneous Raman spectrometer designed for the study of vapors and other low‐density samples is discussed. The high sensitivity is achieved by means of the novel combination of a multipass light cell and a high‐temperature gasdynamic focusing system. A complete description of the apparatus is given, along with the results of a sensitivity test in ambient air, as well as results demonstrating gasdynamic focusing of a vapor and Raman transitions in such a sample.

ISSN:0034-6748    

DOI:10.1063/1.1142537

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The experimental setup for the implementation of a new technique to determine the hyperpolarizability of nonlinear optical molecules in solution is presented. The new technique, hyper‐Rayleigh scattering in solution [K. Clays and A. Persoons, Phys. Rev. Lett.66, 2980 (1991)], has the advantage over the electric‐field‐induced second‐harmonic generation technique that the dipole moment &mgr; and the second hyperpolarizability &ggr; do not have to be independently determined to obtain the first hyperpolarizability &bgr;. No electric field is needed to lower the intrinsic symmetry of the isotropic solution, leading to a simpler cell design and a simpler local field factor. The internal reference method, when applicable, completely eliminates the local field factor. With the technique presented, values of the first hyperpolarizability &bgr; of 23×10−30esu forpara‐nitroaniline (PNA), 105×10−30esu for 4‐methoxy‐4’‐nitrostilbene (MONS), and 95×10−30esu for 4‐hydroxy‐4’‐nitrostilbene (HONS) dissolved in chloroform have been obtained.

ISSN:0034-6748    

DOI:10.1063/1.1142538

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The use of a rotating analyzer ellipsometer is proposed to measure the spectral variation of the transverse Kerr magneto‐optic effect. A low inductance coil is placed close to the sample in such a way that an alternating magnetic field is applied in the plane of the sample and perpendicular to the plane of incidence. First the quantities &psgr; and &Dgr; are measured in the conventional way. For the magneto‐optic effect the magnetization is varied at a high frequency. The analyzer and polarizer are fixed at specified angles while the magneto‐optic signal is measured with a lock‐in detector. The data are used to determine the real and imaginary parts of the magneto‐optic coefficients and their relative sign. It is shown how to calculate from this measurement the value of the off‐diagonal elements of the dielectric tensor.

ISSN:0034-6748    

DOI:10.1063/1.1142539

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Practical realization of the spectrometer based on the cyclotron emission sources is presented. It is shown that it can be used for transmission measurements in the range from 35 to 110 cm−1with resolution up to 1.3 cm−1. Performances of the spectrometer are demonstrated by its application to the studies of impurity and free‐electron states in two‐dimensional structures.

ISSN:0034-6748    

DOI:10.1063/1.1142540

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have constructed a silicon photodiode detector for use with a glancing‐emergence‐angle (GEA) geometry useful for obtaining fluorescence EXAFS spectra from thick specimens with concentrated absorbing species. We present a description of the detector and the results of tests, including dark‐noise tests, EXAFS spectra from a standard sample, and a comparison to an ion chamber also in the GEA configuration. Data obtained from the two detectors are comparable in quality, making the diode detector a preferable choice for this application due to factors such as simplicity of construction and compact size. The diodes also have potential for significant further improvement in the quality of the signal due to their high quantum efficiency if the dark noise can be reduced. We present suggestions for achieving this in future generations of the detector.

ISSN:0034-6748    

DOI:10.1063/1.1142541

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A diamond anvil cell suitable for high‐pressure NMR experiments in a cryostat is described. Inside a rhenium gasket pressures up to 8.3 GPa could be generated. With this apparatus the pressure dependence of the Knight shift and of the self‐diffusion coefficient in metallic lithium and sodium has been measured (as published elsewhere).

ISSN:0034-6748    

DOI:10.1063/1.1142542

出版商:AIP    

年代:1992

数据来源: AIP