Absorption tumbling

Monson P R and McClain W M 1970 Polarization dependence of the two-photon absorption of tumbling molecules with application to liquid 1-chloronaphthalene and benzene J. Chem. Rhys. 53 29-37... 

Pigment used for dry blending is dried overnight at 150°C in a vacuum oven to remove absorbed gases and moisture. It is screened through a 149-p.m (100-mesh) screen directly onto the cubes, which are roUed or tumbled for at least 15 min. The pigmented resin is stored in an airtight container to prevent absorption of moisture. 

AATCC methods for determining water repeUency are AATCC 22 (spray test) and AATCC 70 (tumble jar dynamic absorption test). In the spray test, water is sprayed against the taut surface of the test specimen to produce a wetted pattern the size of which depends on the repeUency of the fabric. Evaluation is by comparing the pattern with a series of patterns on a standard chart. The latter method evaluates the percentage by weight of water absorbed by a sample after dynamic exposure to water for a specified period of time. 

The dynamic absorption test measures the resistance of fabrics to wetting by water, not the repeUency of the total fabric surface. A weighed portion of fiber, yam, or fabric is tumbled ia water for 20 minutes it is then removed and reweighed to determine the percentage of water absorbed (AATCC Test Method 70). 

Polyatomic molecules have more complex microwave spectra, but the basic principle is the same any molecule with a dipole moment can absorb microwave radiation. This means, for example, that the only important absorber of microwaves in the air is water (as scientists discovered while developing radar systems during World War II). In fact, microwave spectroscopy became a major field of research after that war, because military requirements had dramatically improved the available technology for microwave generation and detection. A more prosaic use of microwave absorption of water is the microwave oven it works by exciting water rotations, and the tumbling then heats all other components of food. 

In this section we shall detail the analytical derivation of the absorption spectrum for a magnetic species in a triplet spin state tumbling in a viscous disordered liquid. This an ytical structure consists of the sum of product of continued fractions. The standard Mori structure of Eq. (2.19) is recovered in the absence of orienting potentials. 

The steady-state fluorescence anisotropy/polarization method is also simple and relies on the fact that the probe molecule will tumble rapidly in solution when free, but will have restricted motion upon binding to a macromolecule. Optical excitation of the probe by polarized light will result in preferential absorption by those molecules whose absorption transition dipole is parallel to the electric field vector direction of the light. The subsequent fluorescence will be partially polarized. The definitions of anisotropy (r) and polarization (P) are [188]... 

Anistropy measurements are based on the photose-lective excitation of fluorophores by plane-polarized light. In an isotropic medium, the fluorophores are randomly oriented. Upon excitation with polarized light, those fluorophores whose absorption transition dipole is aligned parallel to the electric vector of the excitation, will be preferentially excited. If the molecule rotates and tumbles out of this plane during the excited state, light is emitted in a different plane from the excitation light. The intensity of the emitted light can be monitored in vertical and horizontal planes and thus, fluorescence anisotropy (r) and polarization ( ) are defined by ... 

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