Focal diameter

For a given light flux of a laser source, the flux of the Raman radiation is inversely proportional to the diameter of the focus of the laser beam at the sample. This means that an optimized Raman sample is a micro sample (Schrader and Meier, 1966 Schrader, 1980). The minimum focal diameter of the laser beam is of the order of the wavelength... 

Particle diameter is much less than diflEraction-limited beam focal diameter... 

The focal diameter of the IR beam is about O.S nun by adjustable rectangular apertures, the beam may be confined further to the desired sample area. Strictly speaking, the IR microscope is operated as a microscope only in optical mode, there creating a magnified image of the sample. In IR mode, the image is created at a 1 1 scale on a narrow band MCT detector with a sensitive area of about 250 x 25 pm. ... 

The shock diagnostic laser pulses typically examine the aluminum surface opposite the substrate. If we call the substrate side the front of the target, then the shock emerges from the back at some time after the drive pulse is absorbed at the front of the aluminum layer. The aluminum layer thickness and the shock velocity determine the shock transit time. Each shock driving laser pulse (ca. 100 pm in focal diameter at the target) destroys the sample (after times much longer than our experiments) at that particular location. A series of experiments can be... 

For the large-focal-diameter electron beams associated with medical x-ray sources, the heat dissipation is considered to occur at the surface and the analytical geometry is that of a disk-heating... 

A beam of a TEMqo laser (Sect. 5.3) with a Gaussian intensity profile is focused to a diffraction-limited spot with the diameter d — 2kf/D by an adapted lens system with the focal length / and the limiting aperture D. For example, with flD= I at = 500 nm, a focal diameter of J 1.0 xm can be achieved with a corrected microscope lens system. This allows the spatial resolution of single cells and their selective excitation by the laser. 

The electrons emitted by the electron gun are focused on the specimen by the Wehnelt cylinder and two to three electromagnetic lenses. As the narrowly focused electron beam strikes the specimen surface, it has a focal diameter of 2-10 nm. A sweep generator is controlled in such a way that the electron beam scans the specimen surface line-by-line and point-by-point. The electron beam also sweeps across a cathode-ray tube. These two motions of the electron beam are synchronized so that each point on the specimen surface is depicted on the screen. The image on a second screen is recorded by a camera. 

Notably, matrix microinjection overcomes the resolution limit imposed by the MALDI laser focal diameter. Numerous other methods serve a similar purpose including laser and mechanical... 

The minimal focal diameter of the laser beam can be in the order of the wavelength of the laser radia-... 

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