Supersonic vibration

Finally, one must realize that, whatever sophisticated electrodes and potentiometers one uses, their proper functioning may be disturbed by the adsorption of adventitious substances such as proteins or surface-active agents and by precipitation or film formation on the electrode surface, unless this is prevented by supersonic vibration or another cleaning procedure. 

Fig. 14. Tarnishing of copper in iodine vapor. Ordinate thickness of tarnishing film, measured interferometrically abscissa time in minutes. Curve 1 with influence of supersonic vibrations (coupled to a supersonic drive, 300 kHertz) curve 2 without supersonic vibrations.

Finally, there should be some mention of the influence of supersonic vibrations on the tarnishing of metals. As in all previous experiments, no other factor (e.g., temperature) but the intended one was altered. The thickness of the tarnishing layers was determined interferometrically. It will be seen from the figure that the influence is of considerable magnitude, a fact that will be of some interest in the study of the mechanism... 

The coagulation of smoke by. supersonic vibrations. Trans. Faraday Soc.f 32 (Part 8) 1111-1115. 

It has long been known that bacterial luminescence is intimately associated with the cells (165), and there is yet no certain evidence that luminescence has been observed apart from the living bacteria. Various means of disrupting cell structure—cytolytic agents, osmolysis, autolysis, mechanical grinding, supersonic vibration—apparently destroy the capacity for luminescence (138), although the activity of certain enzyme systems,... 

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

Molecular clusters are weakly bound aggregates of stable molecules. Such clusters can be produced easily using supersonic expansion, and have been extensively studied by both electronic and vibrational spectroscopy [146,... 

Raman scattering is normally of such very low intensity that gas phase Raman spectroscopy is one of the more difficult techniques. This is particularly the case for vibration-rotation Raman spectroscopy since scattering involving vibrational transitions is much weaker than that involving rotational transitions, which were described in Sections 5.3.3 and 5.3.5. For this reason we shall consider here only the more easily studied infrared vibration-rotation spectroscopy which must also be investigated in the gas phase (or in a supersonic jet, see Section 9.3.8). 

It might be thought that the small number of molecules in a typical supersonic jet or beam would seriously limit the sensitivity of observation of the spectra. Flowever, the severe rotational cooling which may be produced results in a collapsing of the overall intensity of a band into many fewer rotational transitions. Vibrational cooling, which greatly increases the population of the zero-point level, concentrates the intensity in few vibrational transitions, and these two effects tend to compensate for the small number of molecules. 

Fluorescence excitation spectra of fairly large molecules in a supersonic jet are simplified, vibrationally, due to depopulation of low-lying vibrational levels in the ground electronic... 

More commonly, the resonant two-photon process in Figure 9.50(c) is employed. This necessitates the use of two lasers, one at a fixed wavenumber Vj and the other at a wavenumber V2 which is tunable. The first photon takes the molecule, which, again, is usually in a supersonic jet, to the zero-point vibrational level of an excited electronic state M. The wavenumber of the second photon is tuned across the M to band system while, in principle, the photoelectrons with zero kinetic energy are detected. In practice, however, this technique cannot easily distinguish between electrons which have zero kinetic energy (zero velocity) and those having almost zero kinetic energy, say about 0.1 meV... 

An ingeneous method to circumvent this problem was first devised by Zewail and colleagues, who took advantage of the vibrational and rotational cooling properties and collision-free conditions of the supersonic... 

We use laser photofragment spectroscopy to study the vibrational and electronic spectroscopy of ions. Our photofragment spectrometer is shown schematically in Eig. 2. Ions are formed by laser ablation of a metal rod, followed by ion molecule reactions, cool in a supersonic expansion and are accelerated into a dual TOE mass spectrometer. When they reach the reflectron, the mass-selected ions of interest are irradiated using one or more lasers operating in the infrared (IR), visible, or UV. Ions that absorb light can photodissociate, producing fragment ions that are mass analyzed and detected. Each of these steps will be discussed in more detail below, with particular emphasis on the ions of interest. 

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