Photoabsorption molecular

Figure Bl.6.12 Ionization-energy spectrum of carbonyl sulphide obtained by dipole (e, 2e) spectroscopy [18], The incident-electron energy was 3.5 keV, the scattered incident electron was detected in the forward direction and the ejected (ionized) electron detected in coincidence at 54.7° (angular anisotropies cancel at this magic angle ). The energy of the two outgoing electrons was scaimed keeping the net energy loss fixed at 40 eV so that the spectrum is essentially identical to the 40 eV photoabsorption spectrum. Peaks are identified with ionization of valence electrons from the indicated molecular orbitals.

Before progressing, it is useful to review the dynamics of typical molecular systems. We consider three types scattering (chemical reaction), photodissociation, and bound-state photoabsorption (no reaction). 

Bound-state photoabsorption, direct molecular dynamics, nuclear motion Schrodinger equation, 365-373... 

Rhodopsin is a transmembrane protein linked to 11-c/s-retinal, which, on photoabsorption, decomposes to opsin and all-f/a/75-retinal. Rhodopsin has a molecular weight of about 40,000. Its C-terminus is exposed on the cytoplasmic surface of the disk, and its sugar-containing... 

Berkowitz, J. Atomic and Molecular Photoabsorption, Absolute Total Cross Sections. Academic Press San Diego, 2002 1-350. 

These lines of results using repair-deficient strains suggest that inner-shell photoabsorption, followed by the Auger effect, more efficiently produces a nonrepairable type of damage than x-rays with other energies. However, studies to find or identify these types of damages at the molecular level have not yet been successful so far. 

O. Zobay, G. Alber, Periodic orbits and molecular photoabsorption, J. Phys. B 26 (1993)... 

The nature of the molecular system implements a change in the physical mechanism of the photoabsorption process. Once again we may, however, employ the golden rule expression. We use it in a general sense to express the absorption rate in the form of ... 

A single-particle effect that adds features in the X-ray absorption spectrum of molecules not present in that of atoms is the shape resonance (74, 75). (In the case of solids this effect, caused by a modification of the density of states due to the presence of the other atoms in the molecule, is automatically accounted for in band calculations.) Localization of the excited electron inside the molecule in states resulting from an effective potential barrier located near the electronegative atoms in the molecule causes strong absorption bands in free molecules and near the inner-shell ionization limits of positive ions in ionic crystals (74). Consequently, molecular inner-shell spectra depart markedly from the corresponding atomic spectra. The type of structure of an inner-shell photoabsorption spectrum depends on the geometry of the molecule, the nature of its ligands, etc., and can sometimes be used to determine the structure of the molecule. 

Recently in our laboratory we have initiated a program to study the photoabsorption processes of metal vapors throughout the UV and EUV region. Our research interests are (1) to obtain the absolute cross section measurement of atomic and molecular metal vapors, (2) to study the photoionization processes of molecular metal species, and (3) to study the photodissociation processes of molecular metal ions. Several experimental methods such as the heat-pipe absorption spectroscopy, photoionization mass spectroscopy, and electron-ion coincidence technique, will be used in the study. This report summarizes our first experiment using heat-pipe absorption spectroscopy. 

The photoabsorption of atomic and molecular potassium were measured in the extreme ultraviolet (EUV, 50-70 nm) and ultraviolet (UV, 210-400 nm) region. In the first experiment the... 

The symmetrical process of hole transfer from the photoexcited acceptor to the donor is described in an analogous way, and can be driven by photoabsorption in spectral regions where the acceptor can be photoexcited but not the donor. This route requires that the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the acceptor be smaller than the energy gap of the donor. 

XANES (X-ray Absorption Near-Edge Strueture) is X-ray absorption spectroscopy for the lower energy region than EXAFS (Extended X-ray Absorption Fine Structure). It is sensitive to the local atomic arrangement around the absorbing atom and to the chemical states because the low energy electrons emitted through the photoabsorption are affected by details of the molecular potential (1). 

In the method, the differential equation for the continua is resolved in the same way as for the molecular orbital method. Sufficient basis sets represent the continuum wavefunctions in the molecular region and then my depends only on the density of the discretized states. Therefore, the density curves derived from smoothing the oscillator strengths of the states correspond to the photoabsorption spectra (10, 21). In the present work, the Lorentzian curve with the peak width (FWHM) of 3.0cV was used as a combined function of <5 and the smoothing. Though the discretized states depend on the choice of basis set, the spectrum obtained is practically independent of this, fhis was confirmed by using different sizes of the basis sets. 

The uniaxial PF2/6 alignment can be quantified in terms of the mean-field theory discussed previously. The degree of alignment in equilibrium (f2) is a function of the number-averaged molecular weight (M ) as described by Eq. 6. This prediction has been studied by photoabsorption in [55] and there it has been shown that the solid angle T2 is expressed in terms of the dichroic ratio in absorption (R) as... 

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