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Grounded probe technique

As also already shown in Figures 5.8 to 5.16 the validity of Eqs. (5.18) and (5.19) has been confirmed by several laboratories using the Kelvin probe technique, as well as UPS (via electron cutoff energy) and in a semiquanti-tative manner via the PEEM technique. Experiment has also clearly shown that the validity of these equations, which include only thermodynamic properties, does not depend on which, if any, electrode is grounded.31 The same is clearly tme for electrochemical promotion in general, as should be obvious to every electrochemist reader. [Pg.225]

The ground electronic state of 139La160 is X2S+ audits electronic spectrum involving the excited B2Y,1 has been studied by Doppler-free laser-induced fluorescence by Bacis, Collomb and Bessis [85] and by Bernard and Sibai [86]. Both states have therefore been well characterised and the system is ideal for radiofrequency/optical double resonance, as described by Childs, Goodman, Goodman and Young [87]. They used a collimated molecular beam, with the laser pump/probe technique described elsewhere in this chapter. [Pg.938]

Other classes of reactions that have received much attention are proton transfer and electron transfer reactions. These processes can often be initiated by light. This characteristic has made it possible to monitor their time evolution by ultrafast pump-probe techniques. An example is the acid-base reaction of 1-naphthol with ammonia. On the ground electronic surface... [Pg.57]

Since the first experiments on the I-CN [21] bond cleavage and the wavepacket oscillations between the ionic and covalent potentials in the photodissociation of Nal [22, 23], pump-probe techniques have been applied to a wide range of important photochemical processes. However, the data obtained Ifom such experiments are often difficult to interpret and theoretical modeling is needed to get further insight into the excited state dynamics of the systems of interest at the atomistic level. In this context, the development of efficient and accurate computational methods for the description of ground and excited electronic states of mid-size molecular systems in a balanced way [24, 25], has greatly facilitated the theoretical study of photochemical processes. [Pg.3]

The solvation shells of ions may not be spherically symmetrical, a phenomenon that occurs at the surfaces of solutions. The solvent molecules may then polarize the ions, even if they are monatomic, and thus affect their properties. However, in the bulk of the solutions, monatomic ions reside in a spherically symmetrical field and are themselves little affected by the solvent. This is not necessarily the case for polyatomic ions, even for those that have a globular shape. This effect is most noted in the vibrational and rotational relaxation times of polyatomic ions. The relaxation is measurable by the pump/probe technique, where the laser beam at the wave-number of the ground state is followed after a short interval by a probe beam at the level of the excited state, following its exponential decay. [Pg.186]

Radiometry. Radiometry is the measurement of radiant electromagnetic energy (17,18,134), considered herein to be the direct detection and spectroscopic analysis of ambient thermal emission, as distinguished from techniques in which the sample is actively probed. At any temperature above absolute zero, some molecules are in thermally populated excited levels, and transitions from these to the ground state radiate energy at characteristic frequencies. Erom Wien s displacement law, T = 2898 //m-K, the emission maximum at 300 K is near 10 fim in the mid-ir. This radiation occurs at just the energies of molecular rovibrational transitions, so thermal emission carries much the same information as an ir absorption spectmm. Detection of the emissions of remote thermal sources is the ultimate passive and noninvasive technique, requiring not even an optical probe of the sampled volume. [Pg.315]

Conjugated polymers are centrosymmetric systems where excited states have definite parity of even (A,) or odd (B ) and electric dipole transitions are allowed only between states of opposite parity. The ground state of conjugated polymers is an even parity singlet state, written as the 1A... PM spectroscopy is a linear technique probing dipole allowed one-photon transitions. Non linear spectroscopies complement these measurements as they can couple to dipole-forbidden trail-... [Pg.422]

Knowledge on the plasma species can be obtained by the use of plasma diagnostics techniques, such as optical emission spectroscopy (OES) and mass spectroscopy (MS). Both techniques are able to probe atomic and molecular, neutral or ionized species present in plasmas. OES is based on measuring the light emission spectrum that arises from the relaxation of plasma species in excited energy states. MS, on the other hand, is generally based on the measurement of mass spectra of ground state species. [Pg.236]

Needle contact probes These are probably the simplest and least expensive devices. A needle is mounted on a micrometer and insulated from ground, except for the tip, by a nonconducting varnish. The needle is moved into the wavy liquid film flows along a conducting plate, which is grounded. As the needle is moved, the fraction of time during which contact with the liquid top takes place is noted, and is related to the probability that the film thickness is greater than some value. This technique can provide information on the minimum, maximum, and mean thickness with reasonable reliability. [Pg.196]


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See also in sourсe #XX -- [ Pg.63 , Pg.191 ]

See also in sourсe #XX -- [ Pg.63 , Pg.191 ]

See also in sourсe #XX -- [ Pg.63 , Pg.191 ]




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Probe techniques

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