On the assignment of the HOMO in UF6

Electron spectroscopic measurements provide strong evidence that the HOMO in UF₆ is of t_1g symmetry and not t_1u which has been generally assumed.     

On the structure of the water dimer

The infrared spectrum of the mixed water dimer H₂O·D₂O has been observed at 20 K in a nitrogen matrix. The O-H(D) … O stretching vibrations are found to be slightly shifted compared to the corresponding vibrations in (H₂O)₂ and (D₂O)₂. The results are interpreted as evidence for the open dimer structure of Tursi and Nixon.     

Selective deacetylation of aromatic acetates by aminolysis

Pyrrolidine was shown to deacetylate aromatic acetyl groups considerably faster than aliphatic groups.     

Computer search for small complete caps

A computer search method for finding small complete caps inPG(d,q) is considered. The problem is formulated as a combinatorial optimization problem to which record-to-record travel, a stochastic local search method, is applied. Several new complete caps are found and upper bounds on the number of points in the smallest complete caps inPG(d,q) are tabulated for small parameters.This research was supported by the Academy of Finland.     

Low temperature diffusion and trapping of muons in aluminium: New experiments and comparison with theory

The low-temperature diffusion experiments in aluminium have been extended to measurements onAlSi,AlGe andAlGa. The systematic study of Al with various impurities now shows that the trapping rate at temperatures below 2 K (described by a T^−0.7 law) is directly related to the elastic distortion caused by each specific doping element. The overall diffusion behaviour in Al from 0.05 to 200 K can be described by the Kondo theory, only by assuming a low Debye frequency parameter, and if an additional T¹ diffusion rate is included in the intermediate temperature range.     

A complex between ammonia and chlorine studied at 20°K in a nitrogen matrix

UV and IR spectra of ammonia and chlorine codeposited in a nitrogen matrix at 20°K have been recorded. An intense absorption band round 2500 Å has been observed. An IR-active chlorine stretch frequency of about 460 cm^?1 and small shifts on the ammonia absorptions were determined. The results are discussed in terms of a charge transfer complex between ammonia and chlorine. From the complex shifts for ammonia and ammonia-d₃ an opening up of the HNH bond angle on complexing by about 3.6° has been calculated.     

Macrocyclic π-systems with C2-symmetry as the sum of π-systems with hückel and möbius topology

The π-system of a macrocycle with twofold rotation symmetry and 2N conjugated π-electron can conveniently be regarded as the sum of two cyclic N π-electron systems having Hückel and Möbius topology, respectively.     

Low-temperature electron transfer in bacterial photosynthesis

The role of a continuous medium frequency distribution of the Debye form in low-temperature thermal electron transfer processes is investigated. When the electrons are strongly coupled to the medium (the medium reorganization energy is 0.2–0.4 eV) a temperature-independent rate constant is predicted from zero temperature up to over 100 K and with far-infrared Debye frequencies. This is compatible with the experimentally observed low-temperature branch in the Arrhenius relationship of the electron transfer from cytochrome c to excited bacteriochlorophyll, Bch⁺, in bacterial photosynthesis. However, in order to reproduce the high-temperature branch, of finite activation energy, additional activation of intramolecular modes of higher frequencies must be assumed. An intramolecular mode of a coupling constant of 8–9 and a frequency of about 400 cm^?1 can account for this branch. Finally, the estimated electron exchange integral is about 10^?4 eV, indicating that the process is strongly a none diabetic.