Polarized laser excitation

E.E.B. Campbell, H. Schmidt, I.V. Hertel, Symmetry and angular momentum in collisions with laser excited polarized atoms. Adv. Chem. Phys. 72, 37 (1988)... 

In spite of the high polarity of PA6, identification of additives was also feasible in formulations of PA6/additive dissolutions, although with decreased sensitivity. Hostavin N 20, Irganox B 1171, Tinuvin 320 and Tinuvin 350 can be determined in PA6 in technical concentrations, although the sensitivity is less than for nonpolar polymers, such as polyolefins. This was tentatively explained as follows. In a nonpolar polymer matrix, the electronically excited polar additive molecule can easily be desorbed. In the polar polyamide matrix, desorption of the additives is hindered by strong polar interactions (e.g. hydrogen bridges) between the excited analytes and the polymer matrix. This hinders selective desorption of the additives by laser irradiation. However, in a polymer/additive matrix-modified solution, evaporated to dryness, the interactions between the polar... 

Various reactions in which the reactants are in particular vibrational and rotational states have been investigated and state-to-state kinetics have been studied. Two procedures have been used in these investigations. Brooks and coworkers first employed the molecular beam method for studying the state-to-state kinetics. The reactants molecules are put into desired vibrational and rotational states by laser excitation and identified the states by their fluorescence. In molecular beam experiments, it is possible to control the translational energy and mutual orientation of the reactants and to determine the degree of polarization of the rotational angular momentum of the product. 

Polarized Raman spectra from the alkali fluorides LiF, NaF and CsF habe been observed with argon laser excitations by Evans and Fitchen 09). These spectra are of interest as an extreme test of lattice dynamics theories and polarizability models. 

In the simulations presented here, we assume that a pump laser excites the molecule to either the vibrationless, or specific vibrational levels of the Si electronic state. The diffraction pattern is measured by scattering the electron beam off the excited molecules on a time scale shorter than the rotational motion of the molecules, i.e. on a time scale less than about 10 ps. The diffraction pattern is measured in the plane perpendicular to the electron beam. The diffraction patterns shown here are for an excitation laser polarization parallel to the detector plane, and perpendicular to the electron beam. Since the electronic transition dipole moment of s-tetrazine is perpendicular to the aromatic ring, this pump-pulse polarization selects preferentially those molecules that are aligned with the aromatic plane parallel to the electron beam. 

VI. POLARIZATION STUDIES IN QUENCHING PROCESSES FROM LASER-EXCITED Na (3p)... 

As shown by Fig. 8.14, in most Stark spectra above the classical ionization limit there is never one isolated resonance but, more often, an irregular jumble of them. For example, in Fig. 8.15 we show the observed22 and calculated23 Na spectra near the ionization limit in a field E = 3.59 kV/cm.22 The experimental spectrum of Fig. 8.15(a) was obtained by Luk et al.22 by exciting a Na beam with two simultaneous dye laser pulses from the 3s1/2 to 3p3/2 state and then to the ionization limit. Both lasers were polarized parallel to the field, and the ions... 

The first measurements of Na nd fine structure intervals using quantum beats were the measurements of Haroche et al41 in which they detected the polarized time resolved nd-3p fluorescence subsequent to polarized laser excitation for n=9 and 10. Specifically, they excited Na atoms in a glass cell with two counterpropa-gating dye laser beams tuned to the 3s1/2—> 3p3/2 and 3p3/2— ndj transitions. The two laser beams had orthogonal linear polarization vectors et and e2 as shown in Fig. 16.9. 

The dipole is, in principle, a space vector but the response is usually concentrated along a prefered axis. In the case of a laser excitation, for example, the dipole motion is concentrated along the laser polarization axis (when a linearly polarized laser is used) which me will then take as z axis. Note that in the definition Eq. (9), the space integration is limited to an analyzing volume V. We take in practice a region with a broad margin of 2-3 Wigner-Seitz radii rs around the cluster volume [24], For details on the interest and impact (or rather the lack of impact) on the spectral analysis, as well as on the ionization (section 2.2.2), see [21],... 

FIGURE 5 33 CpL (upp curve) total luminescence (lower curve) for a 0.05 M aqueous solution of Tb(III) with the ligand shown. CPL is observed from this racemic mixture following circularly polarized laser excitation at 488 nm 6... 

The simplest method consists of investigating the collisional depopulation of a laser excited rovibronic level, i.e. of measuring the rates and cross-sections of the collisional relaxation of its population bPo- The relaxation rate Tk of polarization moments bPQ of various rank K may be represented, in the case of isotropic collisions, as follows ... 

Auzinsh, M.P. (1987). Polarization of laser-excited fluorescence of diatomic molecules and the magnetic-field effect, Opt. Spectrosc. 

Tamanis, M.Ya., Ferber, R.S. and Shmit, O.A. (1976). Optical orientation of diatomic molecules under circularly polarized laser excitation, Opt. Spectrosc. (USSR), 41, 548-550. 

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