Absorption and emission due to localized excitons in CsI:Na

The absorption spectra and the characteristic emission and excitation spectra of CsI:Na bulk crystals at temperatures between 300 K and 4.2 K are reported. Localized exciton energies were calculated by considering a Born-Haber cycle. The results were compared with the experimental results and the origins of the absorption bands were identified. The characteristic emission spectrum consists of two bands, one peaking around 4200 Å, the other around 3800 Å. The corresponding excitation spectra show that this emission is due to the recombination of a relaxed exciton which was created by transferring an electron from an iodine ion to a substitutional sodium ion in an otherwise perfect CsI lattice.     

Forced common turning point procedure and excitation in slow HH(1s) collisions

It is found that the forced common turning point procedure is satisfactory for treating the excitation of hydrogen atoms by slow protons evan at an energy of relative motion as low as 30 eV.     

Conductance of tetraalkylammonium salts in propylene carbonate at 25°C

Conductance measurements of 12 quaternary ammonium salts in propylene carbonate (PC) have been made at 25°C. The cations were either tetramethylammonium, tetraethylammonium, or tetra-n-butylammonium, and the concentrations of salt varied from about 2×10^–4 to 5×10^–3 M. The data were analyzed by the equation of Pitts. The results showed that the benzoate, nitrobenzoate, and pentachlorophenolate salts are completely dissociated. The nitrophenolate, chlorophenolate, methylsulfonate, and nitrate salts are only slightly associated (K _A from 2.5 to 6.5), while the acetate, phenylacetate, and nitrophenolate salts display somewhat more extensive association, with ionpair association constants from 17 to 45. Limiting molar conductances for the anions were derived. The factors affecting ionic mobilities in this dipolar aprotic solvent are discussed.On leave 1973–1975 from the University of Gdask, Poland.     

A new reagent for polypeptide synthesis: mu-oxo-bis-(tris-(dimethylamino)-phosphonium)-bis-tetrafluoroborate.

The products 1 and 2 (X = OTs) have been isolated from the reaction between hexamethylphosphortriamide and p-toluene sulfonic anhydride and the latter converted into μ-oxo-bis-[tris-(dimethylamino)-phosphonium]-bis-tetrafluoroborate 2 (X = BF₄). This is a practical reagent for the formation of the peptide link. Where racemisation is possible via oxazolone formation this can be decreased by the addition of 1-hydroxybenzotriazole or N-hydroxysuccinimide. These additives may also increase the efficiency of condensation at glycine and proline residues.