Resonance effects ultraviolet

Ultraviolet photoelectron spectroscopy (UPS) involves ionization of valence electrons which probes metal-ligand bonding and change with ionization (from resonance effects as photon energy is scanned through metal M edge), thus directly studying redox processes in metal complexes allows for study of closed shell systems which are inaccessible via electronic absorption spectroscopy ... 

The physico-chemical properties of monosubstituted benzenes were discussed in terms of inductive and resonance effects [9-1 ], the last being very important in the interpretation of electronic spectra and of dipole moments. In vapour phase, the near ultraviolet spectra of monosubstituted benzenes are shifted towards longer wave lengths as compared to the benzene spectrum [15]. Sponer et al [16] have established such a shift of, 035 cm for aniline. We established the position of the electronovibrational component max vapour phase, at 39,6 0 cm for benzene, and at 3, 870 cm... 

Gronowitz et al. have discussed the effects of substituents on chemical reactivity and on ultraviolet (XJV), infrared (IR), and nuclear magnetic resonance (NMR) spectra in terms of simple resonance theory,They assume resonance structures (1-5) to contribute to a —I—M (Ingold s terminology) 2-substituted thiophene, resonance forms (6-10) to the structure of a drI-fM 2-substituted thiophene, forms (11-16) to a —I—M 3-substituted thiophene, and forms (17-22) to a I -M 3-substituted thiophene. 

We have limited our investigations to the action of gamma-rays and fast neutrons on aromatic, alicyclic, aliphatic, and ionic compounds. The absorption coefficients for these types of radiation have an order of magnitude of lO /cm which is particularly adequate. Shallow penetrating radiations would only alter the superficial layers and would obviously not be able to affect the intensity of the quadrupole line substantially. This is for instance the case for ultraviolet light which has been shown to be unable to produce any effect on the resonance line of iodoform (CHI3 3Sg)... 

For our purpose, it is convenient to classify the measurements according to the format of the data produced. Sensors provide scalar valued quantities of the bulk fluid i. e. density p(t), refractive index n(t), viscosity dielectric constant e(t) and speed of sound Vj(t). Spectrometers provide vector valued quantities of the bulk fluid. Good examples include absorption spectra A t) associated with (1) far-, mid- and near-infrared FIR, MIR, NIR, (2) ultraviolet and visible UV-VIS, (3) nuclear magnetic resonance NMR, (4) electron paramagnetic resonance EPR, (5) vibrational circular dichroism VCD and (6) electronic circular dichroism ECD. Vector valued quantities are also obtained from fluorescence I t) and the Raman effect /(t). Some spectrometers produce matrix valued quantities M(t) of the bulk fluid. Here 2D-NMR spectra, 2D-EPR and 2D-flourescence spectra are noteworthy. A schematic representation of a very general experimental configuration is shown in Figure 4.1 where r is the recycle time for the system. 

Nuclear magnetic resonance studies on meso-ionic l,2,4-triazol-3-ones (200) were used to examine their relationship to the alternative l,3,4-oxadiazol-2-imine structure (153). The effect of solvent polarity upon the ultraviolet spectrum of anhydro-3-hydroxy-1,4-diphenyl-1,2,4-triazolium hydroxide (200, R = = Ph, R = H) has been discussed... 

The carbonyl stretching frequencies of a number of heteroannular ferro-cenecarboxylic acids have been measured (41). The spectral shifts vary in the direction expected from the electronic effects of the substituent groups, and parallel the effects of these substituents on the acid constants. Little and Clark have also demonstrated resonance interaction of the ferrocenyl group in ferro-cenylazobenzenes by measuring shifts in the absorption maxima in the visible and ultraviolet spectra (49). 

The evolution of the spectrum of SN 1987A in the ultraviolet was extremely rapid and unique for an SN II. For the first day or so the spectrum was dominated by broad features from 1200 to 3200 A which were unlike any previous observed supernova (Wamsteker et al. 1987, Kirshner et al. 1987). By the third or fourth day, the spectrum resembled that of previously observed SN la and SN lb. Wheeler et al. (1986) attribute the UV spectra of SN I to resonant line scattering of Fe II, and hence a similar effect is presumably at work in SN 1987A. SN 1987A faded rapidly until it could no longer be seen at short wavelengths with the IUE satellite. 

---