Optical spectroscopy ground states

Specific optical rotation values, [a], for starch pastes range from 180 to 220° (5), but for pure amylose and amylopectin fractions [a] is 200°. The stmcture of amylose has been estabUshed by use of x-ray diffraction and infrared spectroscopy (23). The latter analysis shows that the proposed stmcture (23) is consistent with the proposed ground-state conformation of the monomer D-glucopyranosyl units. Intramolecular bonding in amylose has also been investigated with nuclear magnetic resonance (nmr) spectroscopy (24). 

Early experimental spectroscopic investigations on Rg- XY complexes resulted in contradictory information regarding the interactions within them and their preferred geometries. Rovibronic absorption and LIF spectra revealed T-shaped excited- and ground-state configurations, wherein the Rg atom is confined to a plane perpendicular to the X—Y bond [10, 19, 28-30]. While these results were supported by the prediction of T-shaped structures based on pairwise additive Lennard-Jones or Morse atom-atom potentials, they seemed to be at odds with results from microwave spectroscopy experiments that were consistent with linear ground-state geometries [31, 32]. Some attempts were made to justify the contradictory results of the microwave and optical spectroscopic studies, and... 

Knowledge on the plasma species can be obtained by the use of plasma diagnostics techniques, such as optical emission spectroscopy (OES) and mass spectroscopy (MS). Both techniques are able to probe atomic and molecular, neutral or ionized species present in plasmas. OES is based on measuring the light emission spectrum that arises from the relaxation of plasma species in excited energy states. MS, on the other hand, is generally based on the measurement of mass spectra of ground state species. 

The direct proof that H is present in certain centers in Ge came from the substitution of D for H, resulting in an isotopic energy shift in the optical transition lines. The main technique for unraveling the nature of these defects, which are so few in number, is high-resolution photothermal ionization spectroscopy, where IR photons from an FTIR spectrometer excite carriers from the ls-like ground state to bound excited states. Phonons are used to complete the transitions from the excited states to the nearest band edge. The transitions are then detected as a photocurrent. 

The chemical properties of BA have been studied in detail (Lapin et al., 1984). Low temperature epr spectroscopy shows clearly that the ground state of BA is the triplet (3BA). The zero field parameters (Table 3) reveal some details of this structure. When the irradiation is performed at 4.6 K in a 2-methyltetrahydrofuran glass no epr signals from radical species are apparent. The optical spectrum under these conditions shows absorptions (Table 4) which disappear when the glass is warmed. From these findings the absorption bands are assigned tentatively to 3BA. This conclusion is strongly supported by results from laser flash photolysis experiments. 

The epr spectrum of AN clearly shows that it is a ground-state triplet carbene (Devolder et al., 1972). The optical absorptions of this species were assigned at low temperature (Bourlet et al., 1972) and confirmed recently by laser spectroscopy (Tables 3 and 4) (Field and Schuster, 1985). The chemical properties of AN are now readily recognized as those characteristic of a ground-state triplet carbene where intersystem crossing to the singlet is slow (Cauquis and Reverdy, 1975a,b). 

Diphenylmethylene is certainly the most exhaustively studied of the aromatic carbenes. Low temperature epr spectroscopy (Trozzolo et al., 1962) clearly established the ground state of this carbene as the triplet. The optical spectrum of the triplet was recorded first in a 1,1-diphenylethylene host crystal (Closs et al., 1966) and later in frozen solvents (Trozzolo and Gibbons, 1967). 

The yttrium monocarbide molecule was only recently observed under high resolution by Simard et al. (37) using Jet-cooled optical spectroscopy. The ground electronic state was determined to be an 0=5/2 state, which was consistent with the ab initio calculations of Shim et al. (38) who predicted a 11 ground state for YC in CASSCF calculations. The experimental work of Simard et al. yielded estimates for both the bond length and harmonic frequency of YC. In addition to their CASSCF calculations. Shim et al. (38) also reported results from mass spectrometric equilibrium experiments, which resulted in a bond dissociation energy of Do = 99.0 3.3 kcal/mol. The results from the present work are shown in Table I. An open-shell coupled cluster singles and doubles... 

ESR and optical spectroscopy. Their stmctures are closely related to their parents this manifests itself in an interesting simple relationship between the PE spectra of ground-state parent molecules and the electronic spectra of their radical cations The excitation energies, AE, of radical cations correspond approximately to differences in the ionization energies. A/, of the parent molecules (cf. Fig. 6.5). ... 

In atomic absorption spectroscopy (AAS), the optical absorption of atoms in their ground state is measured when the sample is irradiated with the appropriate source. 

Aqueous [Ru"(bpy)3]2+ is a model system for Metal-to-Ligand Charge Transfer (MLCT) reactions. Its excited state properties have been readily studied with optical spectroscopies [15,16]. However, little is known about its excited state structure, which we investigated via time-resolved x-ray absorption spectroscopy. The reaction cycle is described by Fig. 3 (where the superscripts on the left hand side of the ground and excited state compounds denote the... 

---