- Email: [email protected]
Influence of chemical substitution on energy band structure of polyfluoroethylenes
Localized molecular orbital Jr. and M.H. Whangbo.
studies
in momentum
space. I. Compton
profiles
of 1s core electrons
and hydrocarbons
- V.H. Smith
The calculations of momentum space properties for the polyatomic molecules CH 4, C2 Ha, and Cz He using localized molecular orbitals of double zeta quality basis sets are presented. The LMO analysis shows that localized and canonical core electrons have different momentum space properties, and that in agreement with the experimental data of Eisenberger and Marra one can distin&wish the momentum properties of the CC single and double bonds. The effect of environment on a bond is seen by comparing the CH bond in these three molecules. The concept of electron pair size is introduced as a quantitative guide for interpreting momentum space properties. Reactive scattering K. Schmidt.
of H and D atoms.
II. Isotope
effect
on the angular
distribution
of H, D + NOa - H. Haberland,
P. Rohwer
and
The chemical reactions of hydrogen and deuterium atoms with nitrogen dioxide (NOz) have been studied with crossed molecular beams. Angular and velocity distributions have been measured. The angular distribution peaks at small angles and shows a pronounced isotope effect; only = 24% of the available energy goes into translation. Although four very deep potential wells (2.1 eV) exist in the potential hypersurface no statistical complex is formed. The reaction can probably be described as intermediate between direct and complex scattering. Dependence of impurity zero-phonon F.P. Burke and G.J. Small.
band thermal
broadening
and shift on impurity
site and vibron
level in organic
crystals
Experimental results on the thermal broadening and shifts of impurity zero-phonon bands in some organic mixed crystals are reported and interpreted in terms of the electron-phonon interaction. Attention is focused on the variation of the thermal broadening and line shift parameters with (1) impurity site in a system exhibiting several energetically different impurity sites and with (2) the vibron level in a given final electronic state of the impurity. Experiments were conducted over a temperature range which ensures that hot vibron transitions are negligible. Data from the 5600 A ’B 1 + ‘Al transition of 2-phenyl-1-monoazaazulene in pterphenyl show that the variations of the above parameters with impurity site are as large as the variations of the same between different chemical systems. No dependence of the thermal broadening parameters on the impurity vibron level is observed for the above system or the 7000 A ’ Br + ’Al transition of azulene in naphthalene. It is shown that, within the adiabatic (electronnucleus) and harmonic approximations, the zero-phonon band spectral shape function arising from the electron-phonon interaction should be independent of the final vibron level of the impurity transition. Absorption, crystals
fluorescence and phosphorescence spectra of the singlet and triplet at low temperatures - R.M. Hochstrasser and D.S. King.
states of s-tetrazine
in the crystal
and in mixed
The electronic absorption, fluorescence and phosphorescence spectra of s-tetrazine at low temperatures (4.2 - 1.5”K) are reported and analyzed in the neat crystal and in several mixed crystals. The ‘B,, - ‘Ag (nn*) origin is at 18 414 i 5 cm-t for neat tetrazine. In the mixed crystals several sites are identified. The lowest energy origin is at 17 453 cm-t for tetrazine in pyrazine; 17 701 cm-t in pyrimidine; and 17 676 cm-’ in pyridazine. The 3Bsu - ’Ag(nn*) origin is at 14 096 f 2 cm-’ for the neat cry.+ tal. The phosphorescence lifetime of neat tetrazine is measured to be 96.8 * 2.1 IJS at 4.2 and 1.8”K. All the spectra are predominately composed of members of progressions in a single totally symmetric mode (usa) built upon site origins and vibrational fundamentals. The vsa interval is: 743 (’ Ag), 715 c3BsU), and 709 cm-‘(’ B3U) in the neat tetrazine crystal; 732 (’Ag) and 705 cm-’ (’ B3U) in pyrazine host, 737(‘Ag) and 701 cm-1(‘B3U) in pyrimidine host, and 732 (‘Ag) and 703 cm-1(1B3U) in pyridazine host mixed crystals. All emission spectra may be analyzed by O(i) - (v’,&) a(i), i indicating the observed sites. Semi-classical
three-dimensional
model
for vibrational
energy
transfer
in diatomic
molecules
- G.B. Sorensen.
A semi-classical model for calculation of rate-constants for vibrational excitation in diatomic gases at low temperatures (below 1000°K) is suggested. The model has been tested by its ability to predict the relaxation times of hydrogen (rHa) in the temperature region 40-1000°K. The agreement with experimental values is excellent. The isotopic ratio rDa/rHz as a function of temperature is predicted. Influence
of chemical
Extended Hiickel mental confirmations
substitution
on energy
band structure
of polyfluoroethylenes
band structures of six fluorinated compounds by ESCA spectroscopy are suggested.
derived
- J. Delhalle.
from linear polyethylene
are presented.
Possible
experi-
studies
in momentum
space. I. Compton
profiles
of 1s core electrons
and hydrocarbons
- V.H. Smith
The calculations of momentum space properties for the polyatomic molecules CH 4, C2 Ha, and Cz He using localized molecular orbitals of double zeta quality basis sets are presented. The LMO analysis shows that localized and canonical core electrons have different momentum space properties, and that in agreement with the experimental data of Eisenberger and Marra one can distin&wish the momentum properties of the CC single and double bonds. The effect of environment on a bond is seen by comparing the CH bond in these three molecules. The concept of electron pair size is introduced as a quantitative guide for interpreting momentum space properties. Reactive scattering K. Schmidt.
of H and D atoms.
II. Isotope
effect
on the angular
distribution
of H, D + NOa - H. Haberland,
P. Rohwer
and
The chemical reactions of hydrogen and deuterium atoms with nitrogen dioxide (NOz) have been studied with crossed molecular beams. Angular and velocity distributions have been measured. The angular distribution peaks at small angles and shows a pronounced isotope effect; only = 24% of the available energy goes into translation. Although four very deep potential wells (2.1 eV) exist in the potential hypersurface no statistical complex is formed. The reaction can probably be described as intermediate between direct and complex scattering. Dependence of impurity zero-phonon F.P. Burke and G.J. Small.
band thermal
broadening
and shift on impurity
site and vibron
level in organic
crystals
Experimental results on the thermal broadening and shifts of impurity zero-phonon bands in some organic mixed crystals are reported and interpreted in terms of the electron-phonon interaction. Attention is focused on the variation of the thermal broadening and line shift parameters with (1) impurity site in a system exhibiting several energetically different impurity sites and with (2) the vibron level in a given final electronic state of the impurity. Experiments were conducted over a temperature range which ensures that hot vibron transitions are negligible. Data from the 5600 A ’B 1 + ‘Al transition of 2-phenyl-1-monoazaazulene in pterphenyl show that the variations of the above parameters with impurity site are as large as the variations of the same between different chemical systems. No dependence of the thermal broadening parameters on the impurity vibron level is observed for the above system or the 7000 A ’ Br + ’Al transition of azulene in naphthalene. It is shown that, within the adiabatic (electronnucleus) and harmonic approximations, the zero-phonon band spectral shape function arising from the electron-phonon interaction should be independent of the final vibron level of the impurity transition. Absorption, crystals
fluorescence and phosphorescence spectra of the singlet and triplet at low temperatures - R.M. Hochstrasser and D.S. King.
states of s-tetrazine
in the crystal
and in mixed
The electronic absorption, fluorescence and phosphorescence spectra of s-tetrazine at low temperatures (4.2 - 1.5”K) are reported and analyzed in the neat crystal and in several mixed crystals. The ‘B,, - ‘Ag (nn*) origin is at 18 414 i 5 cm-t for neat tetrazine. In the mixed crystals several sites are identified. The lowest energy origin is at 17 453 cm-t for tetrazine in pyrazine; 17 701 cm-t in pyrimidine; and 17 676 cm-’ in pyridazine. The 3Bsu - ’Ag(nn*) origin is at 14 096 f 2 cm-’ for the neat cry.+ tal. The phosphorescence lifetime of neat tetrazine is measured to be 96.8 * 2.1 IJS at 4.2 and 1.8”K. All the spectra are predominately composed of members of progressions in a single totally symmetric mode (usa) built upon site origins and vibrational fundamentals. The vsa interval is: 743 (’ Ag), 715 c3BsU), and 709 cm-‘(’ B3U) in the neat tetrazine crystal; 732 (’Ag) and 705 cm-’ (’ B3U) in pyrazine host, 737(‘Ag) and 701 cm-1(‘B3U) in pyrimidine host, and 732 (‘Ag) and 703 cm-1(1B3U) in pyridazine host mixed crystals. All emission spectra may be analyzed by O(i) - (v’,&) a(i), i indicating the observed sites. Semi-classical
three-dimensional
model
for vibrational
energy
transfer
in diatomic
molecules
- G.B. Sorensen.
A semi-classical model for calculation of rate-constants for vibrational excitation in diatomic gases at low temperatures (below 1000°K) is suggested. The model has been tested by its ability to predict the relaxation times of hydrogen (rHa) in the temperature region 40-1000°K. The agreement with experimental values is excellent. The isotopic ratio rDa/rHz as a function of temperature is predicted. Influence
of chemical
Extended Hiickel mental confirmations
substitution
on energy
band structure
of polyfluoroethylenes
band structures of six fluorinated compounds by ESCA spectroscopy are suggested.
derived
- J. Delhalle.
from linear polyethylene
are presented.
Possible
experi-