Absorption linearly polarized

Steady-State Fluorescence Depolarization Spectroscopy. For steady state depolarization measurements, the sample is excited with linearly polarized lig t of constant intensity. Observed values of P depend on the angle between the absorption and emission dipole moment vectors. In equation 2 (9), Po is the limiting value of polarization for a dilute solution of fluorophores randomly oriented in a rigid medium that permits no rotation and no energy transfer to other fluorophores ... 

Reflection-Absorption IR spectroscopy (RAIRS) where the linearly polarized IR beam is specularly reflected from the front face of a highly reflective sample, such as a metal single crystal surface (Figure 3.1(a)). This is also sometimes referred to as IRAS (IR reflection absorption). The IR beam comes in at grazing angle (i.e. almost parallel to the surface), and although absorption bands in RAIRS have intensities that are some two orders of magnitude weaker than in transmission studies on... 

Based on experiments with linearly polarized light, Mayer also concluded that the photoreceptor is arranged in a dichroic fashion close to the cell wall. The electrical dipole moment for the absorption of bluelight lies parallel to the cell wall, but is probably random with respect to the normal of the cell wall. In the first experiment, the cells were irradiated with bright light. Clearly, the chloroplasts separate from the walls, which are parallel to the -vector and exhibit a banded pattern (Fig. 17, left). However, in weak polarized light the chloroplasts tended to move close to those walls parallel to the -vector (Fig. 17, right). 

The concept of transition moment is of major importance for all experiments carried out with polarized light (in particular for fluorescence polarization experiments, see Chapter 5). In most cases, the transition moment can be drawn as a vector in the coordinate system defined by the location of the nuclei of the atoms4 therefore, the molecules whose absorption transition moments are parallel to the electric vector of a linearly polarized incident light are preferentially excited. The probability of excitation is proportional to the square of the scalar product of the transition moment and the electric vector. This probability is thus maximum when the two vectors are parallel and zero when they are perpendicular. 

If the incident light is linearly polarized, the probability of excitation of a chro-mophore is proportional to the square of the scalar product MA.E, i.e. cos2 0A, 8 being the angle between the electric vector E of the incident light and the absorption transition moment MA (Figure 5.2). This probability is maximum when E is parallel to MA of the molecule it is zero when the electric vector is perpendicular. 

Probing Metalloproteins Electronic absorption spectroscopy of copper proteins, 226, 1 electronic absorption spectroscopy of nonheme iron proteins, 226, 33 cobalt as probe and label of proteins, 226, 52 biochemical and spectroscopic probes of mercury(ii) coordination environments in proteins, 226, 71 low-temperature optical spectroscopy metalloprotein structure and dynamics, 226, 97 nanosecond transient absorption spectroscopy, 226, 119 nanosecond time-resolved absorption and polarization dichroism spectroscopies, 226, 147 real-time spectroscopic techniques for probing conformational dynamics of heme proteins, 226, 177 variable-temperature magnetic circular dichroism, 226, 199 linear dichroism, 226, 232 infrared spectroscopy, 226, 259 Fourier transform infrared spectroscopy, 226, 289 infrared circular dichroism, 226, 306 Raman and resonance Raman spectroscopy, 226, 319 protein structure from ultraviolet resonance Raman spectroscopy, 226, 374 single-crystal micro-Raman spectroscopy, 226, 397 nanosecond time-resolved resonance Raman spectroscopy, 226, 409 techniques for obtaining resonance Raman spectra of metalloproteins, 226, 431 Raman optical activity, 226, 470 surface-enhanced resonance Raman scattering, 226, 482 luminescence... 

In frequency regions where absorption is small the two indices of refraction , and n2 give rise to the phenomenon of double refraction. One of the most common uses for this property is in making wave retarders such as quarter-wave plates incident light linearly polarized with equal x and y field components is phase shifted upon transmission because of the two different phase velocities c/w, and c/n2. An entire field, usually referred to as crystal optics, arises out of this and further applications of crystal anisotropy. 

Based on the preceding results, we can say that linearly polarized light from the band-gap absorption region can induce either transitory changes or crystallization transformation in amorphous Sbj Sei alloys. These two phenomena critically depend on exposure, show threshold behavior, and seem to arise from apparently different mechanisms defect states or some kind of structural units given preferential orientation under the action of linearly polarized light. 

Interpretable Polarization. Since C02 is a linear molecule, the IR polarization of its asymmetric stretching mode is particularly easy to interpret. In the absence of resonant interactions with modes of neighboring molecules (see below), it is safe to assume that the oriented gas model holds, and that the absorption of polarized light is maximum in the direction of the long axis [52]. The polarization of the bending mode can also be interpreted, although we have not used it as much. 

Linear dichroism is defined as the differential absorption of linearly polarized light (Eq. 6). 

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