Photoelectron spectroscopic study molecules

He I photoelectron spectroscopic studies of the electronic structure of 2(3//)-furanone (4a) and 2(5//)-furanone (5a) were found to be consistent with their chemical stabilities. The IP (9.67 eV) of the HOMO of 2(3H)-furanone is significantly lower than the IP (10.65 eV) of the HOMO of the 2(5//)-furanone. Calculations for both molecules showed that the total energy of 5a is lower than that of 4a (94MI2). At room temperature, 2(3//)-furanone (4a), which is an unstable molecule, is formally converted into the 2(5//)-furanone (5a). This conversion involves a [1.3][Pg.277]

Ll Cl" " (Figure 12) was the most abundant species, and hence the easiest to measure. A reasonably linear segment is apparent over ca. one decade, although this curve is less steep than in the case of Li. This may reflect the more complex Boltzmann population of states for this tetratomic molecule, where a pre-exponential factor is necessary. The departure from linearity is also less abrupt, and occurs at ca. 10.20 eV. We take this to be the adiabatic I.P. of Li2Cl2. Our earlier photoelectron spectroscopic studies (18) yielded 10.22 and 10.17 eV for this quantity, employing two alternative methods of extrapolation. Hence, the inference seems quite plausible that departure from linearity on the semi-logarithmic plot yields a value very close to the adiabatic ionization potential. 

Physical Aspects.—A photoelectron spectroscopic study of perfluoro-2,3-dimethyl-but-2-ene, and cis- and /rans-perfluorobut-2-ene, where the vertical w ionization potentials are 12.61, 11.46, and 11.55 eV, respectively, indicates a planar carbon skeleton for these molecules. A careful gas-phase electron-diffraction study of the six fiuoroethylenes has produced the parameters shown in Scheme 1. Care is needed in this type of study, since the C C and C-F bond lengths obtained tend to be... 

I. Novak, B. Kovac, L. Klasinc, V.A. Ostrovski, Nitrogen lone pair interactions in organic molecules a photoelectron spectroscopic study. Speetroc. Acta Pt. A-Molec. Biomolee. Spectr. 59(8), 1725-1731 (2003)... 

Spectroscopy provides one of the few tools available for probing the inner workings of molecules. Infrared and Raman spectroscopies provide information from which force constants and information about charge distributions can be obtained. Ultraviolet spectroscopy gives information on the nature of the electronically excited states of molecules, and is directly connected with their photochemical transformations. Photoelectron spectroscopy gives information on the nature of the radical cations that may be formed by ionization of a molecule, and NMR spectroscopy can give information on the hybridization associated with a given bond. As a result of the level of information that may be obtained, there have been a number of spectroscopic studies. 

In conclusion, we present a spectroscopic study of nn excitation in trans-Stilbene in a molecular beam experiment. The excitation involves a 1+1 REMPI scheme following the interaction of the molecule with femtosecond UV laser pulses. When the excitation is resonant with the origin of the intermediate Si state, the measured photoelectron distribution reveals a maximum probability for the 0-0 transition. For higher photon energies (266nm) the photoelectron spectrum exhibits a rather complex distribution, due to the excitation of an alternate (C-C) stretching mode. 

As a first step toward answering this question, it seems reasonable to investigate a high-symmetry polyatomic. BH3 is an obvious candidate, given its D3h equilibrium geometry (experimentally verified by photoelectron-spectroscopy studies of BH3 [38] and by gas-phase spectroscopic observations of the neutral molecule itself [39][40]). Besides, its small size makes all-electron OBS-GMCSC calculations on it easily feasible, nowadays, even on a run-of-the-mill Personal Computer. Moreover, the fact that BH3 is an electron-deficient system, and of course that it spontaneously dimerizes to the ever-intriguing diborane, implies that a study of its electronic structure may be of intrinsic interest. 

Many of the important chemical reactions controlling arsenic partitioning between solid and liquid phases in aquifers occur at particle-water interfaces. Several spectroscopic methods exist to monitor the electronic, vibrational, and other properties of atoms or molecules localized in the interfacial region. These methods provide information on valence, local coordination, protonation, and other properties that is difficult to obtain by other means. This chapter synthesizes recent infrared, x-ray photoelectron, and x-ray absorption spectroscopic studies of arsenic speciation in natural and synthetic solid phases. The local coordination of arsenic in sulfide minerals, in arsenate and arsenite precipitates, in secondary sulfates and carbonates, adsorbed on iron, manganese, and aluminium hydrous oxides, and adsorbed on aluminosilicate clay minerals is summarized. The chapter concludes with a discussion of the implications of these studies (conducted primarily in model systems) for arsenic speciation in aquifer sediments. 

Y zeolites an X-ray photoelectron and infrared spectroscopic study using pyridine as a probe molecule", J. Chem. Soc., Far. Trans.I, Sfi 3949-3956. 

N. Sato, H. Inokuchi, K. Seki, J. Aoki, and S. Iwashima, Ultraviolet Photoemission Spectroscopic Studies of Six Nanocyclic Aromatic Hydrocarbons in the Gaseous and Solid States, J. Chem. Soc. Faraday Trans. 2 78, 1929-1936 (1982) N. Sato, K. Seki, and H. Inokuchi, Polarization Energies of Organic Solids Determined by Ultraviolet Photoelectron Spectroscopy, J. Chem. Soc. Faraday Trans., 2 77, 1621-1633 (1981) N. Sato, K. Seki, and H. Inokuchi, Ultraviolet Photoelectron Spectra of Tetrahalo-P-Benzo-quinones and Hexahalobenzenes in the Solid State, J. Chem. Soc. Faraday Trans. 2 77, 47-54 (1981) I. Ikemoto, Y. Sato, T. Sugano, N. Kosugi, H. Kuroda, K. Ishii, N. Sato, K. Seki, and H. Inokuchi, Photoelectron Spectroscopy of the Molecule and Solid of 11,11,12,12-Tetracyanonaphthoquinodimethane (TNAP), Chem. Phys. Lett. 61, 50-53 (1979) K. Seki, S. Hashimoto, N. Sato, Y. Harada, K. Ishii, H. Inokuchi, and J. Kanbe, Vacuum-Ultraviolet Photoelectron Spectroscopy of Hexatricontane (N-C36-H74) Polycrystal A Model Compound of Polyethylene, J. Chem. Phys. 66, 3644-3649 (1977). 

VB or the HMO treatment were necessary, in contrast to the saturated molecules, which could be discussed satisfactorily within purely additive schemes. Although this opinion had been challenged by theoreticians rather early in the game, the realization that electrons occupying saturated molecules are as delocalized as those in n orbitals of unsaturated molecules gained ground mainly after photoelectron (PE) spectroscopic studies had provided a more detailed insight into the orbital structure of saturated molecules, in particular of hydrocarbons. 

ABSTRACT. Photoelectron and mass spectral analyses have become important adjuncts to the recently developed field of multiphoton ionization spectroscopy. Each of the methods are discussed and the significant enhancement in capability provided by their joint application is illustrated by their use in the spectroscopic study of free radicals, molecular ions and transient excited states of molecules. 

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