Stepwise laser excitation techniques

As described previously, (4-benzoylphenoxy)methylnaphthalene exhibited C—O bond dissociation via the T state. The multiple laser excitation technique allows us to study stepwise cleavage of two equivalent bonds in a molecule. To provide clear evidence for the stepwise photocleavage of two equivalent bonds in a molecule, we introduce here two C—O bond cleavages of l,8-bis[ (4-benzoylphenoxy)methyl]naphthalene (l,8-(BPO-CH2)2Np) to give acenaph-thene with the three-step excitation using three-color three-laser flash photolysis (Scheme 2.14) [147],... 

Techniques of stepwise laser excitation and photoionization have been applied to study spectroscopic properties of neutral atoms of lanthanides and actinides. The spectroscopic properties that can be determined include the ionization potential, energy levels, isotope shifts, hyperfine structure, lifetimes of energy levels, branching ratios and oscillator strengths. We discuss the laser methods used to obtain these properties (with emphasis on ionization potentials) and give examples of results obtained for each. The ionization potentials obtained by laser techniques are in eV Ce, 3.3387(4) ... 

This chapter is concerned with experimental investigations of the dynamics of the dissociation of polyatomic neutral molecules carried out by the technique of laser Doppler spectroscopy, in bulk and under crossed-beam condition. Photodissociation is a basic process in the interaction of light with molecules, of interest in itself as an elementary molecular process and also with respect to a variety of applications in different fields. The interest has increased considerably in recent years, first, because the experimental investigation of photodissociation is rapidly advancing by the use of the laser, and second, because the laser makes possible to achieve photodissociation, state, and isotope selectively, by new excitation mechanisms. These are, aside from the common one-photon absorption, stepwise... 

Quite often, monochromatic laser light is applied under conditions of high photon flux, to excite the species of interest efficiently. Under such circumstances, a process that utilizes -photon resonance in the first excitation step and requires additional m photons for final ionization (most frequently m = 1 is encountered) occurs with measurable probability and is of analytical relevance. The technique is called REMPI and uses, as noted, stepwise resonant excitation of an atom or molecule via stable intermediate energy levels. It is usually described as (n- -m)-REMPI spectroscopy the most frequently used (2 -b 1)-REMPI principle is depicted in Figure 5.4. 

The basic technique employs a tunable dye laser for stepwise excitation into a specific Rydberg state (a) with binding energy W. The radiation from a cw single-line CO2 laser is then made incident on these Rydberg atoms. This fixed frequency radiation can induce transitions from the prepared level (a) to still higher levels (b) when the atomic energy difference is Stark tuned into... 

A large number of atoms and molecules have been meanwhile investigated by level-crossing spectroscopy using laser excitation. Because of the available high laser intensity highly excited states can be studied, which have been populated by stepwise excitation (see Sect.8.8). Often resonance lamps are used to excite the first resonance level and a dye laser pumps the next step. Many experiments have been performed with two different dye lasers, either in a pulsed or a cw mode [10.91]. These techniques allow measurement of... 

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