Coherent waves

Transmission electron microscopy (tern) is used to analyze the stmcture of crystals, such as distinguishing between amorphous siUcon dioxide and crystalline quartz. The technique is based on the phenomenon that crystalline materials are ordered arrays that scatter waves coherently. A crystalline material diffracts a beam in such a way that discrete spots can be detected on a photographic plate, whereas an amorphous substrate produces diffuse rings. Tern is also used in an imaging mode to produce images of substrate grain stmctures. Tern requires samples that are very thin (10—50 nm) sections, and is a destmctive as well as time-consuming method of analysis. 

Continuous wave coherent Lyman-a radiation has recently become available [85] so that laser cooling or sensitive shelving spectroscopy of magnetically trapped hydrogen atoms is coming within reach. The ability to work with a small number of atoms is of particular interest for laser spectroscopy of antihydrogen, a goal pursued by the ATRAP and ATHENA collaborations at CERN [8]. 

The absolute intensity of the x-ray wave coherently scattered by a single electron, I, is determined from the Thomson equation ... 

It is worthwhile to note that the charged Bose gas trapped in the double well potential Ua of Eq. 50 behaves as an inverted Josephson junction (N-S-S-N). The super-current, which accompanies the matter wave coherence, is induced between the degenerate resonance states of the adjacent wells at the frequency of the tunnel splitting A response time, as is typical of tunnel junctions (whose frequency cutoff is much smaller than the vibrational frequency even for nano junctions). The coherent oscillations of the Josephson current can be observed by virtue of their slow frequency A V which is robustly controlled by the bias voltage. 

This eq. (3.11) shows that the amplitude of the scattered wave is proportional to the Eourier transform, defined in eq. (5.A17) of the appendix of Ch. 5, of the density p of scattering centres. This is a particularly favourable situation, because the measurements of the amplitudes of the waves coherently scattered in all directions, that is with all possible wavevec-tors 2, allows in principle to calculate by an inverse Eourier transform, also defined by eq. (5.A17) of the appendix of Ch. 5, the density p(f) of scattering centres. This last equation holds for a one-dimensional (ID) Eourier transform, that is a single coordinate x (or 1) and consequently a single conjugate coordinate k (or v in eq. (5.A17)). The extension to a 3D space defined by f and j, 2 is trivial and can be found in any textbook on X-ray. Without entering the details of calculations of inverse 3D Eourier transforms, we nevertheless have to n te that in a coherent scattering experiment the measured quantities are not amplitudes E (eq. (3.11)) of vectors, which are complex quantities, with real and... 

K. Matsubara, U. Tanaka, H. Imago, M. Watanabe All-solid state light source for generation of continious-wave coherent radiation near 202 nm. J. Opt. Soc. Am. B 16, 1668 (1999)... 

K.S.E. Eikema, J. Walt, T.W. Hansch Continuous wave coherent Lyman-alpha radiation. Phys. Rev. Lett. 83, 3828 (1999)... 

Regions on the lunar surface, that are permanently shaded are only found on the South pole (total area about 15000 km ). For detection the lunar surface composition, a radio transmitter was used. Rocky surfaces scatter radio waves randomly, while icy surfaces reflect radio waves coherently like a bicycle reflector. 

Much of the previous section dealt with two-level systems. Real molecules, however, are not two-level systems for many purposes there are only two electronic states that participate, but each of these electronic states has many states corresponding to different quantum levels for vibration and rotation. A coherent femtosecond pulse has a bandwidth which may span many vibrational levels when the pulse impinges on the molecule it excites a coherent superposition of all tliese vibrational states—a vibrational wavepacket. In this section we deal with excitation by one or two femtosecond optical pulses, as well as continuous wave excitation in section A 1.6.4 we will use the concepts developed here to understand nonlinear molecular electronic spectroscopy. 

In view of the foregoing discussion, one might ask what is a typical time evolution of the wave packet for the isolated molecule, what are typical tune scales and, if initial conditions are such that an entire energy shell participates, does the wave packet resulting from the coherent dynamics look like a microcanonical... 

A connnon teclmique used to enliance the signal-to-noise ratio for weak modes is to inject a local oscillator field polarized parallel to the RIKE field at the detector. This local oscillator field is derived from the probe laser and will add coherently to the RIKE field [96]. The relative phase of the local oscillator and the RIKE field is an important parameter in describing the optical heterodyne detected (OHD)-RIKES spectrum. If the local oscillator at the detector is in phase with the probe wave, the heterodyne mtensity is proportional to... 

Albrecht A C, Smith S P, Tan D, Schaertel S A and DeMott D 1995 Ultrasharp spectra and ultrafast timing from noisy coherence in four wave mixing Laser Rhys. 5 667-75... 

Yang M, Kim J, Jung Y and Oho M 1998 Six-wave mixing spectroscopy resonant coherent hyper-Raman scattering J. Chem. Phys. 108 4013-20... 

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