Charge-Transfer Emission Spectroscopy

Krasnopolsky VA, Mumma MJ (2001) Spectroscopy of comet Hyakutake at 80-700 A First detection of solar wind charge-transfer emissions. Astrophys J 549 629-634 Krasnopolsky VA, Bowyer S, Chakrabarti S, Gladstone GR, McDonald JS (1994) First measurement of helium on Mars implications for the problem of radiogenic gases on the terrestrial planets, learns 109 337-351... 

Keywords Biofluids Chemosensors Emission spectroscopy Mechanosensors Optical properties Polarity Rheology Twisted intramolecular charge transfer Viscosity... 

We have reported the first direct observation of the vibrational spectrum of an electronically excited state of a metal complex in solution (40). The excited state observed was the emissive and photochemically active metal-to-ligand charge transfer (MLCT) state of Ru(bpy)g+, the vibrational spectrum of which was acquired by time-resolved resonance Raman (TR ) spectroscopy. This study and others (19,41,42) demonstrates the enormous, virtually unique utility of TR in structural elucidation of electronically excited states in solution. 2+... 

Photoluminescence spectroscopy is used to analyze the electronic properties of semiconducting CNTs [64]. The emission wavelength is particularly sensitive to the tube diameter [65] and chemical defects [66], However, a more dedicated sample preparation is required in order to eliminate van der Waals and charge transfer interactions between bundled CNTs. This can be done via ultrasonication or treatment of the bundles with surfactants that separate individual CNTs and suppress interactions between them [67]. 

Steady-state fluorescence spectroscopy has also been used to study solvation processes in supercritical fluids. For example, Okada et al. (29) and Kajimoto and co-workers (30) studied intramolecular excited-state complexation (exciplex) and charge-transfer formation, respectively, in supercritical CHF3. In the latter studies, the observed spectral shift was more than expected based on the McRae theory (56,57), this was attributed to cluster formation. In other studies, Brennecke and Eckert (5,31,44,45) examined the fluorescence of pyrene in supercritical CO2, C2HSteady-state emission spectra were used to show density augmentation near the critical point. Additional studies investigated the formation of the pyrene excimer (i.e., the reaction of excited- and ground-state pyrene monomers to form the excited-state dimer). These authors concluded that the observance of the pyrene excimer in the supercritical fluid medium was a consequence of increased solute-solute interactions. 

In closing this paragraph we mention the emission spectroscopy of the U6 + ion. This ion shows emission spectra with clear vibrational structure. It is mentioned here because the optical transition is of the charge-transfer type, and the U6+ ion may be described in the present context as a 5f° ion. The vibrational structure in the emission spectra depends strongly on the ligands of... 

It is very interesting to note that a similar idea to the charge transfer of the transition-metal compounds was independently proposed by Benka et al. [36], Urch [37], and Hartmann [38] for the interpretation of the chemical effect of shake-off satellites (transition between multiply ionized states) [39] in x-ray emission spectroscopy. 

---