Zero Electron Kinetic Energy ZEKE spectroscopy

My question to Prof. Gerber is the following Could you please explain the different virtues of femtosecond pump-pulse experiments versus ultrashort zero electron kinetic energy (ZEKE) spectroscopy Do they yield complementary information on the molecular dynamics or are there specific domains where one of them should be preferred with respect to the other ... 

Observation of vibrational structure in the PE spectra of large organometallic molecules is rare because of the large number of vibrational modes that may be excited, the low frequencies of many of the vibrational modes, and the lack of resolution in conventional spectrometers. Techniques such as zero electron kinetic energy (ZEKE) spectroscopy have been successful in resolving vibrational structure on small molecules but have not been successfully extended to organometallics as yet. Those spectra that show vibrational structure have proved informative. 

The fourth technique for electron analysis measures a preselected set of zero or nearly-zero kinetic energy. While first known as TPE spectroscopy, when monochromatic synchrotron light was used, the addition of pulsed, tunable lasers has led to a totally new, extremely promising branch of PES, termed zero electron-kinetic-energy (ZEKE) PES or ZEKE spectroscopy18. We will describe it in detail later. 

Two especially important variants of REMPI (Johnson, et al., 1975) spectroscopy are ionization-dip (Cooper, et al., 1981) and Zero Electron Kinetic Energy (ZEKE) (Miiller-Dethlefs and Schlag, 1991 Merkt, 1997 Signorell and Merkt, 1999) photoelectron spectroscopy. Ionization-dip REMPI spectroscopy is especially useful when one wants to record free<—bound spectra from a single, selectable v, J level. Without such v, J selection, most of the oscillatory structure in a free<—bound spectrum will be washed out. One potential problem with some ionization-dip schemes is that, if the ionization transition originates from the initial level of the free<—bound transition being studied, there is a possibility that the observed linewidths will be distorted by power broadening (especially when the free final state is a weakly predissociated state with linewidth < lcm-1). 

ADE = adiabatic detachment energies ESC A = electron spectroscopy for chemical analysis HOMO = highest occupied molecular orbitals MAES = metastable atom electron spectroscopy MIES = metastable ionization electron spectroscopy OAT = oxygen atom transfer PES = photoelectron spectra PEI = pulsed field ionization PIES = Penning ionization electron spectroscopy QM = quantum-mechanical REMPI = resonantly enhanced multiphoton ionization SC = semiclassical VDE = vertical detachment energies XPS = x-ray photoelectron spectroscopy ZEKE = zero electron kinetic energy Cp = cyclopentadienyl, Ph = phenyl, CeHs Tp =... 

The improved numerical stability of the new deMon2K version also opened the possibility for accurate harmonic Franck-Condon factor calculations. Based on the combination of such calculations with experimental data from pulsed-field ionization zero-electron-kinetic energy (PFl-ZEKE) photoelectron spectroscopy, the ground state stmcture of V3 could be determined [272]. Very recently, this work has been extended to the simulation of vibrationaUy resolved negative ion photoelectron spectra [273]. In both works the use of newly developed basis sets for gradient corrected functionals was the key to success for the ground state stmcture determination. These basis sets have now been developed for aU 3d transition metal elements. With the simulation of vibrationaUy resolved photoelectron spectra of small transition metal clusters reliable stmcture and... 

Zero Electron Kinetic Energy Spectroscopy, ZEKE... 

Abbreviations used in the tables calc = calculated value PT = photodetachment threshold using a lamp as a light source LPT = laser photodetachment threshold LPES = laser photoelectron spectroscopy DA = dissociative attachment attach = electron at-tachment/detachment equilibrium e-scat = electron scattering kinetic = dissociation kinetics Knud=Knudsen cell CT = charge transfer CD = collisional detachment and ZEKE = zero electron kinetic energy spectroscopy. 

ZEKE zero electron kinetic energy spectroscopy... 

ZEKE (zero kinetic energy) photoelectron spectroscopy has also been applied to negative ions [M]. In ZEKE work, the laser wavelengdi is swept tlirough photodetachment thresholds and only electrons with near-zero kinetic energy are... 

Photoelectron spectroscopy (PES, a non-mass spectral technique) [87] has proven to be very useful in providing information not only about ionization potentials, but also about the electronic and vibrational structure of atoms and molecules. Energy resolutions reported from PES are in the order of 10-15 meV. The resolution of PES still prevents the observation of rotational transitions, [79] and to overcome these limitations, PES has been further improved. In brief, the principle of zero kinetic energy photoelectron spectroscopy (ZEKE-PES or just ZEKE, also a nonmass spectral technique) [89-91] is based on distinguishing excited ions from ground state ions. 

Two types of time resolved experiments can be carried out on such a system. The less ambiguous approach is that employed in the stilbene—He study (fig. 10.5) in which a second laser, time delayed from the pump laser, is used to excited the state. Smith and Knee (1993) have used picosecond time resolved TPES spectroscopy in which zero-energy electrons are collected as a function of the probe laser wavelength. [Laser based TPES has also been called zero kinetic energy (ZEKE) electron spectroscopy or pulsed field ionization (PFI) (Muller-Dethlefs and Schlag, 1991)]. Figure... 

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