High-resolution ultraviolet spectrum

In 2000 Remmers et al. [24] used the combination of molecular beam techniques and high resolution laser spectroscopy (inherent line width 3 MHz) to obtain the first information on proton transfer tunneling in any isolated gas phase carboxylic acid dimer. They reported the measurement of a high resolution ultraviolet spectrum of benzoic acid dimer in the gas phase. The spectra showed two... 

In addition to transitions in the ir manifold discussed above, some attention has been given recently to possible o-ir states in the ultraviolet nonradlative transitions from the B2jj state. Callomon et al. (27) have postulated the transitions from higher vibrational levels of B2y to a E2u(high resolution absorption spectrum of vapor phase benzene in the 5.0 eV region. initio (12,28) calculations have predicted the presence of at least one a state (e2 ) lying between two filled ir-molecular orbitals. Photoionization (29,30) experiments, and other evidence (31) appear to agree with the conclusion that a-o-ir transition may be... 

ICP-OES is one of the most successful multielement analysis techniques for materials characterization. While precision and interference effects are generally best when solutions are analyzed, a number of techniques allow the direct analysis of solids. The strengths of ICP-OES include speed, relatively small interference effects, low detection limits, and applicability to a wide variety of materials. Improvements are expected in sample-introduction techniques, spectrometers that detect simultaneously the entire ultraviolet—visible spectrum with high resolution, and in the development of intelligent instruments to further improve analysis reliability. ICPMS vigorously competes with ICP-OES, particularly when low detection limits are required. 

Ultraviolet spectra of Comet Seargent 1978 XV taken from the lUE satellite. Exposure times for the low-resolution spectra are 180 and 165 min. The high-resolution spectrum shows the rotational structure of the (0,0) OH band (from Jackson, W. M., Icarus 41, 147, 1980)... 

The ultraviolet absorption spectrum has an intense band with a maximum below 200 mg and a finely structured long-wavelength band from about 280 to 330 mg (e 308.5 mg = 176 liter/mole cm.). The long wavelength band remains diffuse under high resolution. The shape of this band is unusual, but appears to be a common feature of all the diazirines so far reported (see later) and is reminiscent of the absorption spectrum of 2,3-diazabicyclo[2,2,l]-2-heptene, another molecule containing a strained nitrogen double bond. ... 

When a beam of polychromatic ultraviolet or visible radiation passes through a medium containing gaseous atoms, only a few frequencies are attenuated by absorption. When recorded on a very high resolution spectrometer, the spectrum consists of a number of very narrow absorption lines. 

In principle, ultraviolet-excited photoelectron spectroscopy would be ideally suited for valence-band-structure studies because of its extremely high resolution. However, ultraviolet-photoelectron spectra may not truly represent the band structure being probed because the energy of the ultraviolet source is so low, it tends to induce valence-electron transitions and thereby distort the intensity distribution of the resulting photoelectron spectrum. X-ray excitation, on the other hand, while providing poorer resolution, is essentially free of such distortions. Thus, the two types of photoelectron spectra serve to complement each other and provide a more complete picture of the valence-band structure. 

The photoelectron spectra can be generated using a primary beam of ultraviolet radiation (known as ultraviolet photoelectron spectroscopy (UPS)), or X-rays to yield an XPS spectrum. It can also be generated by synchrotron radiation (SR), in which case the electron spectrometer must be attached to the beam line at a synchrotron facility. UPS is essentially a molecular spectroscopy that provides high-resolution valence band spectra, while XPS is used predominantly to study core level transitions, and also to study valence band electrons. 

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