Negative-ion photoelectron

Dessent C E FI and Johnson M A 1998 Fundamentals of negative ion photoelectron spectroscopy Fundamentals and Applications of Gas Phase Ion Chemistry ed K R Jennings (Berlin Kluwer)... 

Lineberger W C 1982 Negative ion photoelectron spectroscopy Applied Atomic Collision Physics, Vol 5, Special Topics ed FI S W Massey, E W McDaniel and B Bederson (New York Academic)... 

Wenthold P and Lineberger W C 1999 Negative ion photoelectron spectroscopy studies of organic reactive intermediates Accts. Chem. Res. 32 597-604... 

In negative ion photoelectron spectroscopy (NIPES), the reactant is a negative ion, and the upper state is neutral. In this case, the origin can be used to determine the electron affinity. 

Figure 5.1. Schematic potential energy surfaces for the photoelectron spectroscopy experiment. Labels in parentheses refer to negative ion photoelectron spectroscopy.

In select cases, negative ion photoelectron spectroscopy can also be used to investigate reaction transition states.The ideal situation is illustrated in Figure... 

P. G. Wenthold and W. C. Lineberger, Negative Ion Photoelectron Spectroscopy Studies of Organic Reactive Intermediates, Acc. Chem. Res. 1999, 32, 597. 

The singlet-triplet splitting of NH was determined experimentally by spectroscopy of neutral NH and by negative ion photoelectron spectroscopy (PES) of the NH anion. In the latter experiment, the anion NH is prepared in the gas phase and exposed to monochromatic ultraviolet (UV)-laser hght. This photolysis leads to ejection of photoelectrons whose kinetic energies ( k) are analyzed. As the energy... 

Figure 21-8. Schematic of a negative ion photoelectron (photodetachment) spectrometer...

Harding, L. B. Goddard, W. A., Ill Methylene ab initio vibronic analysis and reinterpretation of the spectroscopic and negative Ion photoelectron experiments, Chem. Phys. Lett. 1978, 55, 217-220. 

Four of the most powerful methods presently applied to elucidate metal cluster geometric structure will be presented in the following. These are mass-selected negative ion photoelectron spectroscopy, infrared vibrational spectroscopy made possible by very recent advances in free electron laser (FEL) technology, gas-phase ion chromatography (ion mobility measurements), and rf-ion trap electron diffraction of stored mass-selected cluster ions. All methods include mass-selection techniques as discussed in the previous section and efficient ion detection schemes which are customary in current gas-phase ion chemistry and physics [71]. 

Fig. 1.18. Mass-selected negative ion photoelectron spectra for Au 02 clusters (n = 1,2,4). The line structures in the spectra correspond to the vibrational frequencies of the neutral state in the geometry of the anion. Indicated are also the geometric equilibrium structures of the cluster complexes obtained from DFT calculations [124,125]...

Ion cyclotron resonance (ICR) and flowing afterglow experiments can also be used to derive relative affinities. Neutral beam experiments, where a beam of alkali atoms such as Cs is crossed with a beam of molecules such as PCI3 or (012)2 have been used to derive thermochemistry for anions such as PCli" and Cli", but proper analysis of this type of data is difficult. High-resolution negative ion photoelectron spectroscopy (NIPES) experiments can provide otherwise unobtainable information on hypervalent anions, including precise electron affinities and vibrational frequencies.This technique has limited applicability to hypervalent species with more than three atoms because of vibrational congestion from low-frequency modes. 

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... 

Figure A3.5.3. The negative ion photoelectron spectrometer used at the University of Colorado. The apparatus now contains a UV-buildup cavity inside the vacuum system (not shown in this sketch). 

---