Die Photoelektron‐Spektren der Monohalogenacetylene

Abstract

1073kcinem Fall widersprechen sich die Vorzeichen. Die Chiralitaten der asyminetrischen Zentren bestimmen sich somit zu (3S:llaS:5aR:lObR).Eine Berechnung aller intermolekularen htomabstande ergab keine ungewohnlich starken Kontakte. Der kurzeste intermolekulare Abstand, abgesehen von der ohen beschriebenen interinolekularen Wasserstoffbrucke (Fig. 4), betragt 2,2 zwischen zwei Wasserstoffatomcn. LITERATURVERZEICHNIS S.Summary. The photoelectron spectra of the four monohaloacetylenes X-CEC-H with X = F, C1, Br, I have been recorded. The first four bands of these spectra are assigned (in order of increasing ionization potentials) to the following states: band 1: 211,/2(1), 2111/2(1) ; band 2 : 211,,2(2), 21Zl/2(2); band 3: 2Z+(3); band 4 : 2Z+(4). A correlation diagram based on a simple ZDO-MO model shows that the observed band positions and the size of the splits duc to spin-orbit coupling can be satisfactorily explained in terms of such a model. I t is found that the orbital energies A x of the postulated halogen npA(X)-basis orbitals are a linear function of the ionization potentials I ( X ) of the free atoms X. The validity of the ZDO-MO-model is confirmed by the excellent qualitative agreement between the observed and predicted spacings of the vibrational fine structure of the n-bands. I) 12. Mitteilung iiber Anwendungen der Photoelektron-Spektroskopie. 11. Mitteilung : [l] Dans les publications antCrieures de cette sdrie, il a Ctd montrk que la benzoylation du methyl-1-fluorbne selon Friedel-Crafts en milieu de sulfure de carbone se fait en position 2 [2]; celle du mCthyl-2-fluor6ne, en position 7 [3]; et celle du mdthyl-3-

The Renner-Teller effect in HCCCl+(X̃2Π) studied by zero-kinetic energy photoelectron spectroscopy and ab initio calculations

“…Overview Figure 1 shows an overview of the ZEKE spectrum of HC-CCl obtained in this work along with the previously published conventional photoelectron spectrum. 31 The three strong broad peaks in the conventional photoelectron spectrum are from the first vibrational band (0 0 ), fundamental (2 1 ), and second harmonic excitation (2 2 ) bands of the C≡ ≡C stretching vibrations, respectively. Figure 2 is an expanded view of the ZEKE spectrum, in which the assignments for the peaks and the band origins are indicated.…”

“…The photoelectron spectra of the series were reported in 1970. 31 However, due to the low resolution of the conventional photoelectron spectra, the vibrational structure of the cations was not resolved. Recently, the spin-vibronic structure of HCCI + (X 2 Π) was studied by Merkt and co-workers using high resolution zero-kinetic energy (ZEKE) photoelectron spectroscopy.…”

An Estimate of the Interatomic Distances in Monohaloacetylene Radical Cations from Photoelectron‐spectroscopic Data

“…-- As shown in a previous communication [Z], the PE. spectra of I ( X ) contain two PE.-bands which correspond to an ionisation process (1) in which an electron has been ejected from one or the other of the pairs of top-occupied n-orbitals ~~( 1 ) or nA (2). The index A, which can take the values +1 or -1, refers to the associated angular momentum.…”

“…The index A, which can take the values +1 or -1, refers to the associated angular momentum. The resultant states ?P of the radical cations I + ( X , Y) are 2nn,(l) and zZIn, (2) respectively, with total angular monumentum quantum numbers ISL! = 3/2 or 1/2.…”

“…(4 In the case of I + ( X , M) the symbol ! P stands for the electronic ground state %=zII, (l) or the first electronically excited state A9IICJ (2) [2] of the radical cation. The determination of AR,,(V) is based on a simple and convenient application of the Franck-Condon principle 3 ) .…”