Abstract :
We have established a high-resolution vacuum ultraviolet (VUV) photoionizationphotoelectron facility at the chemical dynamics beamline of the advanced light source. This facility is equipped with a 6.65-m monochromator, which has demonstrated a resolving power of ~ 100,000 in the range of 6-30 eV. This resolving power is close to that achieved in common VUV lasers. Taking advantage of this high-resolution capability, we have developed novel synchrotron based pulsed-field ionization-photoelectron (PFI-PE) schemes, attaining resolutions of 1-5 cm-1 (FWHM), which are also similar to that attained in laser-based PFIPE studies. Most recently, we have introduced a generally applicable PFI-PE-photoion coincidence (PFI-PEPICO) method, making possible the internal state selection for cations to a resolution of 4-5 cm-1 (FWHM) limited only by the PFI-PE measurement. The PFIPEPICO study of the reaction O2+h nu" border=0 src="/.dejavu/.tact/lib1/art410/pcdata/html_gif/charset.gif/bam.gif"O+(4S)+O(3P)+e- demonstrates that the dissociation dynamics of diatomic cations can be examined in specific rotational levels using this method. This study also supports that the dissociation threshold for O+(4S)+O(3P) lies at O2+(b4sigmag-, v+=4, N+=9). In the PFI-PE-PICO study of CH4 (C2H2), we show that the 0 K dissociative photoionization threshold for CH3+ (C2H+) from CH4 (C2H2) can be determined unambiguously by the disappearance energy of the CH4+ (C2H2+) parent ion to an accuracy of ±0.001 eV. These measurements, when combined with accurate ionization energies for CH3, CH4 and C2H2 obtained by PFI-PE measurements, have allowed the determination of highly accurate 0 K bond dissociation energies for H-CH3, H-CH3+, and HC2H+. The PFI-PEPICO study of 2-C3H7X (X=Cl, Br and I) has yielded more accurate values for the heat of formation of C3H7+ and the proton affinity of C3H6.
Keywords :
Lennard-Jones , ZEKE electron spectra , Alkylbenzenes , Ar vdW complexes
