Spectroscopy high resolution, absorption

Microwave spectroscopy is generally defined as the high-resolution absorption spectroscopy of molecular rotational transitions in the gas phase. Microwave spectroscopy observes the transitions between the quantised rotational sublevels of a given vibrational state in the electronic ground state of free molecules. Molecular... 

With the development of more versatile tunable semiconductor lasers in the near infrared, high-resolution absorption spectroscopy in this spectral range has been greatly improved. Magnetic field tuned semiconductor lasers as well as current tunable devices have been used. 

Deep state experiments measure carrier capture or emission rates, processes that are not sensitive to the microscopic structure (such as chemical composition, symmetry, or spin) of the defect. Therefore, the various techniques for analysis of deep states can at best only show a correlation with a particular impurity when used in conjunction with doping experiments. A definitive, unambiguous assignment is impossible without the aid of other experiments, such as high-resolution absorption or luminescence spectroscopy, or electron paramagnetic resonance (EPR). Unfortunately, these techniques are usually inapplicable to most deep levels. However, when absorption or luminescence lines are detectable and sharp, the symmetry of a defect can be deduced from Zeeman or stress experiments (see, for example, Ozeki et al. 1979b). In certain cases the energy of a transition is sensitive to the isotopic mass of an impurity, and use of isotopically enriched dopants can yield a positive chemical identification of a level. 

UV absorption spectroscopy is usually not sensitive enough to monitor ions direetly in the jet. Even if the original ion pair is somehow dissociated in to two separate ions having a eharacteristie absorption, their detection by high-resolution absorption speetroscopy is often impraetieal. The nascent product ions are formed in a large number of quantum states, and the small population of a single state eannot be detected with reasonable signal-to-noise ratio. 

Kocharova N, Leiro J, Lukkari J et al (2008) Self-assembled carbon nanotubes on gold polarization-modulated infrared reflection-absorption spectroscopy, high-resolution X-ray photoemission spectroscopy, and near-edge X-ray absorption fine structure spectroscopy study. Langmuir 24 3235-3243... 

A detailed understanding of both the solid state and surface chemistry has been gready assisted by improved characterization techniques (including X-ray absorption spectroscopy, high resolution electron microscopy, 3D-NMR spectroscopy, and others) and new molecular modeling methods. 

V.G. Avetisov, P. KaiU anen High-resolution absorption measurements using two-tone frequency-modulation spectroscopy with diode lasers. Appl. Opt. 36, 4043 (1997)... 

In this spectral range it is up to now the semiconductor diode laser which has been mostly used for high-resolution laser spectroscopy. After HINKLEY [8.37] had first demonstrated in 1970 the superiority of laser spectroscopy over conventional techniques by a high-resolution absorption spectrum of SFg around 10 ym obtained with a Pb-Sn-Te laser, spectra of numerous molecules have been measured with different diode lasers. A review of the literature up to 1975 can be found in the article by HINKLEY et al. [8.38], more recent examples in [8.39] and [8.39a]. 

The element aluminum-27 occurs at 100% natural abundance and its nucleus has a good receptivity, though its quadrupole moment means that its resonances are broadened relative to those of spin-1/2 nuclei. However, this amounts to only a few hertz or tens of hertz in many cases, with the result that Al has been considered worthy of study from the early days of NMR spectroscopy and has already been the subject of three reviews " and figures in a fourth, and another is to appear. Historically, the first observations were carried out in the derivative mode and with poor quality magnets, which were deemed sufficient for a quadrupolar nucleus but as increasingly improved instrumentation became available, high-resolution absorption... 

Nesbitt D J 1994 High-resolution direct infrared laser absorption spectroscopy in slit supersonic jets intermolecular forces and unimolecular vibrational dynamics in clusters Ann. Rev. Phys. Chem. 45 367-99... 

Some very high resolution or ultrasensitive spectroscopies emerging as of ca 1996 were beam spectroscopy, multiphoton absorption and ionisation, and frequency-modulation spectroscopy (8). Most of these were used primarily for laboratory research as of the mid-1990s, but eventual appHcation to analytical or sensor appHcations is expected. 

Peaks are analyzed separately by their retention times, absorption, and fluorescence properties. RCCs show absorbance maxima near A.500 and 316 nm. For FCCs, UV-Vis specna show two prominent bands near 361 and 320 mn and a luminescence maximum at 436 mn and NCCs show UV-Vis spectra with absorbance maxima near 320 and 210 nm. Nevertheless, as none of these approaches is suitable for elucidating structures, it is necessary to apply additional MS and NMR analyses to fully characterize snuctural features. Electron spray ionization (ESI) and high-resolution EAB mass spectroscopy have been applied to elucidate the molecular formulae of colorless compounds. ... 

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