Nonresonant

As a result, the CRS lineshape is asyimnetric and more complicated due to this nonresonant background interference. 

The nomesonant background prevalent in CARS experiments (discussed above), although much weaker than the signals due to strong Raman modes, can often obscure weaker modes. Another teclmique which can suppress the nonresonant background signal is Raman induced Kerr-efifect spectroscopy or RIKES [96, 97]. 

As already mentioned, electronically resonant, two-pulse impulsive Raman scattering (RISRS) has recently been perfonned on a number of dyes [124]. The main difference between resonant and nom-esonant ISRS is that the beats occur in the absorption of tlie probe rather than the spectral redistribution of the probe pulse energy [124]. These beats are out of phase with respect to the beats that occur in nonresonant ISRS (cosinelike rather tlian sinelike). RISRS has also been shown to have the phase of oscillation depend on the detuning from electronic resonance and it has been shown to be sensitive to the vibrational dynamics in both the ground and excited electronic states [122. 124]. 

Walsh A M and Loring R F 1989 Theory of resonant and nonresonant impulsive stimulated Raman scattering Chem. Phys. Lett. 160 299-304... 

Kummel A C, Sitz G C and Zare R N 1986 Determination of population and alignment of the ground state using two-photon nonresonant excitation J. Chem. Phys. 85 6874-97... 

Dynamic techniques are used to determine storage and loss moduli, G and G respectively, and the loss tangent, tan 5. Some instmments are sensitive enough for the study of Hquids and can be used to measure the dynamic viscosity T 7 Measurements are made as a function of temperature, time, or frequency, and results can be used to determine transitions and chemical reactions as well as the properties noted above. Dynamic mechanical techniques for sohds can be grouped into three main areas free vibration, resonance-forced vibrations, and nonresonance-forced vibrations. Dynamic techniques have been described in detail (242,251,255,266,269—279). A number of instmments are Hsted in Table 8. Related ASTM standards are Hsted in Table 9. 

Fig. 46. Schematic diagram of a dynamic mechanical analy2er based on the nonresonance-forced vibration principle (Rheovibron-type).

When the exciting frequency is nonresonant (distant from any electronic transition), the differential scattering cross section at wavelength X is as in equation 8 ... 

Control is accomplished by controlling the nonresonant portion of the waveform and with a fixed period allowed for the resonant portion of the waveform. 

In Surface Analysis by Laser Ionization (SALI), a probe beam such as an ion beam, electron beam, or laser is directed onto a surfiice to remove a sample of material. An untuned, high-intensity laser beam passes parallel and close to but above the sur-fiice. The laser has sufficient intensity to induce a high degree of nonresonant, and hence nonselective, photoionization of the vaporized sample of material within the laser beam. The nonselectively ionized sample is then subjected to mass spectral analysis to determine the nature of the unknown species. SALI spectra accurately reflect the surface composition, and the use of time-of-flight mass spectrometers provides fast, efficient and extremely sensitive analysis. 

A comparison of the various post-ionization techniques electron-gas bombardment, resonant and nonresonant laser ionization, etc. While some of the numbers are outdated, the relative capabilities of these methods have remained the same. This is a well-written review article that reiterates the specific areas where post-ionization has advantages over SIMS. 

This article discusses why one would choose nonresonant multiphoton ionization for mass spectrometry of solid surfaces. Examples are given for depth profiling by this method along with thermal desorption studies. 

The large variability in elemental ion yields which is typical of the single-laser LIMS technique, has motivated the development of alternative techniques, that are collectively labeled post-ablation ionization (PAI) techniques. These variants of LIMS are characterized by the use of a second laser to ionize the neutral species removed (ablated) from the sample surface by the primary (ablating) laser. One PAI technique uses a high-power, frequency-quadrupled Nd-YAG laser (A, = 266 nm) to produce elemental ions from the ablated neutrals, through nonresonant multiphoton ionization (NRMPI). Because of the high photon flux available, 100% ionization efflciency can be achieved for most elements, and this reduces the differences in elemental ion yields that are typical of single-laser LIMS. A typical analytical application is discussed below. 

When reaction cross sections are suflSciently large over an extended energy range, the entire depth profile may be obtained using a single incident beam energy. This is referred to as nonresonant profiling. 

In nonresonant profiling, the silicon surface barrier detectors that detect the products of the nuclear reaction may also detect signals from incident ions that have been backscattered from the sample. Figure 4 shows an a particle spectrum from the reaction (p, a) along with the signal produced by backscattered... 

Figure 4 Spectrum of diffusion in the mineral olivine ((Mg, Fe)2 SiO ) taken using nonresonant profiling technique with the reaction (p, a) Both the a particles resulting from the nuclear reaction and backscattered protons are collected. Inset shows expanded region of the spectrum, where a yield indicates diffusion of into the material.

Laser Ionization Mass Spectrometry Laser Microprobe Mass Analysis Laser Microprobe Mass Spectrometry Laser Ionization Mass Analysis Nonresonant Multi-Photon Ionization... 

Surface Analysis by Laser Ionization Post-Ionization Secondary Ion Mass Spectrometry Multi-Photon Nonresonant Post Ionization Multiphoton Resonant Post Ionization Resonant Post Ionization Multi-Photon Ionization Single-Photon Ionization... 

Schallstarke, /. intensity of sound, schalltot, a. acoustically dead, nonresonant. Schallverstarkung, /. sound amplification, schsilweich, a. sound-absorbent. 

There are two major classes of problems to be investigated (NA) nonautonomous, and (A) autonomous.15 In each of these two classes appear two subclasses (NR) nonresonance oscillations, and (R) resonance oscillations. The treatment of these cases is slightly different. 

Problem of Poincard (Nonresonance Case).—Now consider Eqs. (6-47) or (6-48), which are sufficiently general to furnish a basis for further discussion of these systems. If p = 0, one has the differential equation of the harmonic oscillator + x = 0 whose solutions we know. As we assume that p is small, Eq. (6-50) differs but little from that of the harmonic oscillator one often says that the two differential equations are in the neighborhood of each other. But from this fact one cannot conclude that their solutions (trajectories) are also in the neighborhood of each other. Let us take a simple example F(t,x,x) — x and compare the two equations x + x = 0 and x + px + x = 0. For the first the trajectories are circles, whereas for the second they are spirals, so that for a sufficiently large t the solutions certainly are not in the neighborhood of each other, although the differential equations are. 

This constitutes the essential difference from the nonresonance case in which one solution p 0) goes into the other (p = 0) without any possible multiplicity of choices. Here, in the resonance case, in view of the multiplicity (family) of periodic solutions for p = 0, one has to narrow down this choice by the conditions stated in Eqs. (6-70). 

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