摘要:

The problem of finding the power spectrum of a physical process consisting of linear superimposed random events is solved under the general condition of events correlated in a Markov chain. The statistical properties of the system are described in terms of a generalized Markov matrix which contains all the information about the correlations existing between elementary events. The conditions for the existence of a line spectrum component are discussed and the line intensity calculated. In paper II, typical examples of application to practical problems are also given.

ISSN:0021-8979    

DOI:10.1063/1.324502

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The application of the theory developed in paper I to problems of physical interest is considered and developed up to the point of finding the correlation matrix of the problem, thus reducing the complete solution to a matter of numerical computation. The considered cases are of rather large generality and refer to (a) fluctuation processes due to carrier trapping, (b) membrane noise, (c) spectral properties of linear atom chains, and (d) fluctuations in quantum systems whose Hamitonian contains an operator which is a random function of time. In the last case, the most general conditions under which the time evolution of a quantum system can be treated as a Markov process will be found and discussed.

ISSN:0021-8979    

DOI:10.1063/1.324503

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An axisymmetric distribution of electrons incident on a carbon target causes heating of the target. The thermal conductivity of the various carbon polymorphs varies rapidly with temperature. We have solved the nonlinear steady‐state heat‐flow problem. We show that type IIb diamond would be an ideal source for carbonKradiation and that such a static target will sustain a power input of 6.5 kW on an area whose diameter is 1 mm and might, with proper design, operate at an even higher power input on the same area. We show that a power input of 6.5 kW at 6.0 kV on the above area would produce carbonKradiation of sufficient intensity so that the exposure time for PMMA (polymethylmethacrylate, an x‐ray resist of extremely high resolution but relatively low sensitivity) is only 1 min for a source‐to‐substrate distance of 2.54 cm.

ISSN:0021-8979    

DOI:10.1063/1.324504

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Flash photolysis of KrF2at 193 nm has been utilized to directly measure the quenching rate constants of KrF(B) molecules by He, Ne, Xe, and NF3. Investigation of the large rate constant measured for the KrF(B)+Xe reaction (≳10−9cm3 sec−1) verified the XeF(B) state to be a product.

ISSN:0021-8979    

DOI:10.1063/1.324505

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The light which is scattered by a surface acoustic wave, upon total internal reflection and at a grazing angle, exhibits a pronounced structure which varies as the polarization of the light is rotated and differs for a free or metallized surface. A theory is presented which accounts accurately for the various line shapes measured on ay‐zLiNbO3crystal.

ISSN:0021-8979    

DOI:10.1063/1.324506

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The pressure and temperature dependence of the Tl‐Hg excimer emission in the visible from an rf excited discharge has been studied. The gain of the system in the blue band at 4585 A˚ is probed with an Ar‐ion laser. With gain sensitivity limited to 1/2% due to beam steering and defocusing effects, the system has no gain.

ISSN:0021-8979    

DOI:10.1063/1.324507

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A gas cell containing SF6was irradiated with pulses of infrared radiation from a CO2laser. The time dependence of the transmittance of this cell is explained theoretically by means of a combination of saturation and heating. Heating effects are important even at SF6pressures below 130 Pa. Intermolecular transfer of vibrational energy must play a major role in delocalizing the heating at pressures below 110 Pa. The transmittance of SF6gas irradiated by a chopped CO2laser beam depends upon the width and spacing of slots in the chopper wheel and upon the rotational frequency of the wheel.

ISSN:0021-8979    

DOI:10.1063/1.324508

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We report on a mode‐locked cw dye laser which reliably produces light pulses as short as 850 fsec. Short‐pulse operation depends critically on the stability and spectral purity of a frequency synthesizer which generates the radio‐frequency signal for the acousto‐optic mode locker of the argon pump laser. The regular axial mode spectrum of the dye laser extends over 500 GHz and can provide an accurate calibration scale for the spectroscopic measurement of large frequency intervals. The high stability of the locked modes has been demonstrated by observing Doppler‐free multiple‐pulse two‐photon spectra of the sodium 3S‐5Stransition linewidths as narrow as 4MHz.

ISSN:0021-8979    

DOI:10.1063/1.324509

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Data are presented showing that quantum‐well (Lz∼200 A˚) AlxGa1−xAs‐GaAs‐AlxGa1−xAs heterostructures, grown by metalorganic chemical vapor deposition, can be operated as lasers on confined‐particle transitions over an unusually large range (&Dgr;&lgr;≳1000 A˚). The bandfilling properties of these quantum‐well heterostructures, which can easily be excited to carrier densities as high asn≳1019/cm3, are described. Quantum‐well laser diodes (x∼0.5) are described that operate (300 K) from the &Ggr; band edge to wavelengths as short as 7700 A˚ (&Dgr;E∼185 meV). Narrow photopumped samples (15–30 &mgr;m) are shown to operate (77 K) as lasers on clearly defined confined‐particle transitions from the band edge to 6980 A˚ (&Dgr;E∼270 meV). On samples from another wafer, laser operation has been observed to 6885 A˚ (&Dgr;E≡h&ngr;−Eg=293 meV). The photoluminescence spectra of these heterostructures extend well into the region of the recently determinedLband minima of GaAs.

ISSN:0021-8979    

DOI:10.1063/1.324494

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The bandfilling and gain behavior of thin (Lz∼400 A˚) In1−xGaxP1−zAsz(x∼0.13,z∼0.29) layers imbedded in InPp‐njunctions, or on one side of the active region of regular quaternary double heterojunctions (x∼0.09,z∼0.20), are described. Bandfilling and spontaneous emission are observed from the quaternary quantum‐well band edge to the band edge of the InP confining layers (&Dgr;Eg∼245 meV, 77 K). Laser operation on confined‐particle transitions can be observed in the range 0<h&ngr;−Eg(InGaPAs) ≲ (2/3) &Dgr;Eg. The reduced gain of a quantum‐well heterostructure is demonstrated by comparison with the behavior of conventional quaternary double heterojunctions (active layer ≳0.1 &mgr;m) grown from the same set of LPE melts. To operate as lasers quantum‐well heterostructures are shown to require greater diode lengths and higher excitation currents, consistent with large bandfilling (in a thin layer) leading to a large spectral spread in the recombination radiation. These effects are demonstrated also on quaternary double heterojunctions of standard active‐layer thickness (≳0.1 &mgr;m) but modified with the inclusion of a quantum well on one side of the active region.

ISSN:0021-8979    

DOI:10.1063/1.324495

出版商:AIP    

年代:1978

数据来源: AIP