Photoelectron spectroscopic study of simple hydrogen-bonded dimers. I. Supersonic nozzle beam photoelectron spectrometer and the formic-acid dimer

In this paper we describe several characteristics of our supersonic nozzle beam photoelectron spectrometer recently constructed for studying hydrogen-bonded dimers in the gas phase by HeI (58.4 nm) radiation. Using this photoelectron apparatus, we have reinvestigated the HeI photoelectron spectrum of the formic-acid dimer (HCOOH)₂ which is well known as a fairly strong doubly hydrogen-bonded dimer. It was found that the (HCOOH)₂ spectrum deduced here from the spectrum of the monomer—dimer mixture considerably differs from that reported by Carnovale et al. in the region beyond 16.5 eV. New spectral assignments are given for four ionization bands beyond 16.5 eV. It is also indicated that the lower bound of the dissociation energy of (HCOOH)₂⁺ is estimated to be 1.0 ± 0.1 eV from the threshold of the dimer band (11.0 eV) obtained in this experiment. This value is considerably smaller than the value of 1.7 ± 0.2 eV recently reported for the water dimer cation (H₂O)₂⁺.     

Theory of diffusion-controlled reaction between non-simple molecules. II

A simplified version of the closure approximation, presented in the preceding paper, is applied to the reaction of rigid or flexible macromolecular systems. Two effects are found to be important for understanding the characteristic features of the reaction rates of these systems: (i) the orientation effect, which expresses the accessibility of the active sites, and (ii) the relaxation effect, which reflects the nature of the brownian motion of the active sites.     

Photoelectron spectra and sum rule consideration: Effect of chlorine substitution on ionization energies for chloroethanes,chloroacetaldehydes and chloroacetyl chlorides

He(I) photoelectron spectra are reported for various series of chlorine-substituted compounds: (a) CH₃CH_3?mCl_m, (b) CH_3?mCl_mCCl₃, (c) CH_3?mCl_mCHO and (d) CH_3?mCl_mCOCl, where m = 1, 2 and 3. In each series it is shown that the total sum of vertical ionization energies over all p-type localized molecular orbitals (LO's) has an excellent linear relationship to the number of substituted chlorine atoms. The differences in the total orbital energy sum by successive chlorine substitutions are found to be 26.7 eV for series a and b and 27.2 eV for series c and d, yielding the corresponding experimental σ_CCl, energies useful for sum rule considerations. The photoelectron spectra of the chloro compounds studied are interpreted with the help of the sum rule as well as CNDO/2 calculations. Orbital correlation diagrams have been constructed for these compounds.     

Molecular theory of the viscoelāstic properties of concentrated polymer solutions

The viscoelastic properties of concentrated polymer solutions are discussed on the basis of the fixed tube model proposed by de Gennes. It is shown that the steady flow viscosity is proportional to M³, where M is the molecular weight, and that the relaxation spectrum exhibits a hump in the relaxation time proportional to M³.     

Theory of diffusion-controlled reaction between non-simple molecules. I

A new vibrational principle is presented for reaction rates of diffusion-controlled chemical reaction. The variational principle is obtained by a modification of the closure approximation of Wilemski and Fixman. The closure approximation is found to correspond to a special choice of the trial function in this formation and to yield a lower bound of the reaction rate. This formulation is found to be especially useful for the analysis of reaction between non-simple molecules, such as macromolecules.     

Relaxationsspektren von nichtlinearen Polymeren

Ohne Zusammenfassung