Photodissociation spectroscopy

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

Krautwald HJ, Schnieder L, Welge KH et al (1986) Hydrogen-atom photofragment spectroscopy photodissociation dynamics of H2O in the B-X absorption band. Faraday Discuss Chem Soc 82 99-110... 

The field of applications of molecular quantum dynamics covers broad areas of science not only in chemistry but also in physics and biology. Historically, due to the fact that the full quantum-mechanical simulation of molecular processes is limited to small systems, molecular quantum dynamics has given rise mainly to important applications of astrophysical and atmospheric relevance. In the interstellar medium or the Earth atmosphere, molecules are generally in the gas phase. Since many accurate spectroscopic data are available, these media have provided various prototype systems to study quantum effects in molecules and to calibrate the theoretical methods used to simulate these effects. In this context, it is not surprising that much theoretical effort is still directed toward modeling the full quantum-mechanical treatment of small molecules. Among others, one can cite the studies of the spectroscopy of water [159-161], and of the spectroscopy, photodissociation. 

Molecular electronic absorption and emission spectroscopy, photodissociation, Raman spectroscopy, and vibrational overtone spectroscopy have been examined from a time-dependent perspective for their implications for potential energy surfaces and dynamics. A semiclassical point of view greatly aids intuitive understanding and computation of these various spectroscopies from limited local and regional knowledge of the potential surface. 

The pioneering use of wavepackets for describing absorption, photodissociation and resonance Raman spectra is due to Heller [12, 13,14,15 and 16]- The application to pulsed excitation, coherent control and nonlinear spectroscopy was initiated by Taimor and Rice ([17] and references therein). 

The temi action spectroscopy refers to how a particular action , or process, depends on photon energy. For example, the photodissociation of 0 with UV light leads to energetic 0+0 fragments the kinetic energy released has been... 

Farrar J M 1993 Eiectronic photodissociation spectroscopy of mass-seiected ciusters soivation and the approach to the buik Cluster Ions ed C Y Ng and i Provis (New York Wiiey)... 

Flowever, in order to deliver on its promise and maximize its impact on the broader field of chemistry, the methodology of reaction dynamics must be extended toward more complex reactions involving polyatomic molecules and radicals for which even the primary products may not be known. There certainly have been examples of this notably the crossed molecular beams work by Lee [59] on the reactions of O atoms with a series of hydrocarbons. In such cases the spectroscopy of the products is often too complicated to investigate using laser-based techniques, but the recent marriage of intense syncluotron radiation light sources with state-of-the-art scattering instruments holds considerable promise for the elucidation of the bimolecular and photodissociation dynamics of these more complex species. 

Ashfold M N R, Mordaunt D H and WIson S H S 1996 Photodissociation dynamics of hydride molecules H atom photofragment translational spectroscopy Adv. Photochem. 21 217-95... 

The earliest molecular beam infrared experiments on Van der Waals complexes used photodissociation spectroscopy a molecular beam is irradiated witli a tunable infrared laser and tire molecular beam intensity is measured as a function of... 

Dyer R B, Einarsdottir 6, Killough P M, Lopez-Garriga J J and Woodruff W H 1989 Transient binding of photodissociated CO to of eukaryotic cytochrome oxidase at ambient temperature. Direct evidence from time-resolved infrared spectroscopy J. Am. Chem. Soc. Ill 7657-9... 

W. M. Kwok and D. L. Phillips, Solvation effects and short-time photodissociation dynamics of CH2I2 in solution from resonance Raman spectroscopy. Chem. Phys. Lett. 235(3-4), 260-267 (1995). 

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... 

Vibrationally mediated photodissociation (VMP) can be used to measure the vibrational spectra of small ions, such as V (OCO). Vibrationally mediated photodissociation is a double resonance technique in which a molecule first absorbs an IR photon. Vibrationally excited molecules are then selectively photodissociated following absorption of a second photon in the UV or visible [114—120]. With neutral molecules, VMP experiments are usually used to measure the spectroscopy of regions of the excited-state potential energy surface that are not Franck-Condon accessible from the ground state and to see how different vibrations affect the photodissociation dynamics. In order for VMP to work, there must be some wavelength at which vibrationally excited molecules have an electronic transition and photodissociate, while vibrationally unexcited molecules do not. In practice, this means that the ion has to have a... 

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