Spectroscopy photofragment

Photofragment spectroscopy.—The analysis of the angular distribution and energies of fragments arising from photodissociation, using polarized light, permits evaluation of the states involved in the dissociation process and an approach towards the ideal experiment in which microscopic reaction rates can be measured, and there has been much increased interest in this phenomenon in the past year, both from an experimental and theoretical standpoint. Papers 

A brief report has appeared on the crossed-beam reaction between Ba and LiCl, using laser-induced fluorescence detection of the BaCl product, which gives a lower bound for the bond-dissociation energy of BaCl of 110 3 kcal mol-1.242 Similar studies on the reactions of alkali-metal dimers with hydrogen atoms and molecules 243 and the photodissociation of alkali-metal iodides244 have been reported. 

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Moseley J and Durup J 1981 Fast ion beam photofragment spectroscopy Annual Review of Physical Chemistry ed B S Rabinovitch, J M Schurr and H L Strauss (Palo Alto, CA Annual Reviews)... 

Moseley J T 1985 Ion photofragment spectroscopy Photodissociation and Photoionization ed K P Lawley (New York Wiley)... 

Boyarkine O V, Settle RDF and Rizzo T R 1995 Vibrational overtone spectra of jet-cooled CFgH by infrared laser assisted photofragment spectroscopy Ber. Bunsenges. Rhys. Chem. 99 504-13... 

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. 

Photofragment spectroscopy is extremely sensitive, but it has the disadvantage that one is only sensitive to absorption that leads to photodissociation. For single-photon experiments, this means that one is restricted... 

Methane-to-methanol conversion by gas-phase transition metal oxide cations has been extensively studied by experiment and theory see reviews by Schroder, Schwarz, and co-workers [18, 23, 134, 135] and by Metz [25, 136]. We have used photofragment spectroscopy to study the electronic spectroscopy of FeO" " [47, 137], NiO [25], and PtO [68], as well as the electronic and vibrational spectroscopy of intermediates of the FeO - - CH4 reaction. [45, 136] We have also used photoionization of FeO to characterize low lying, low spin electronic states of FeO [39]. Our results on the iron-containing molecules are presented in this section. 

Krautwald, H.J., Schnieder, L., Welge, K.H., and Ashfold, M.N. (1986). Hydrogen-atom photofragment spectroscopy, Faraday Discuss. Chem. Soc. 82, 99-110. 

It must be emphasized that this model is only one of a large family inspired by the picture drawn by Herschbach and co-workers, and thus they should not be blamed for its particular faults. We do not wish to imply that it is a necessary consequence of the original picture, but rather we have taken it as a simple illustration of one possible way of integrating unimolecular photofragment spectroscopy results into bimolecuJar dynamic models of electron transfer reactions. More sophisticated... 

Figure 10 The left-hand panel shows the excitation scheme used in a typical doubleresonance overtone photofragment spectroscopy experiment. The particular scheme shown here is used to prepare HOCl molecules with six quanta of OH stretching and many quanta of rotation, just above the dissociation threshold. The right-hand panel depicts sample double-resonance spectra of the HOCl(6ui <— 2vi) band. Each spectrum in the plot originates from a selected (J, K ) rotational state. Courtesy of T. R. Rizzo.

Laser surface chemistry has been used as a basis for many new methods in surface processing, for example, photochemical deposition of metals and photochemical etching of solid substrates, which are potentially useful techniques for the microelectronics industry (1-3). However, molecular dynamical studies of UV photodissociation of adsorbates on solid surfaces have been very scarce (4-7). We have studied UV laser photodissociation of small molecules on solid surfaces using photofragment spectroscopy. 

DROPS double-resonance overtone photofragment spectroscopy... 

Photofragment spectroscopy of 03 between 457.9—752.5 nm has determined energy partitioning in the and O2 photofragments formed from ground and vibrationally excited (in the v, symmetric stretching mode) parent molecules. Predissociation of the h Lg and / rig states of has been studied. 

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