Difference mass spectrum, potential energy

The energy difference between diazirine and diazomethane, interesting from the point of view of their isomerism, came from MS measurements (63JCP(39)3534). The appearance potentials of the CH2 ion, common to both compounds, yielded a difference in heats of formation of 125kJmor A strong peak in the mass spectrum of 3-chloro-3-methyl-diazirine (50) with relative mass 55 was ascribed to the methyldiazirinium ion (51). 

In summary, ionisation potentials, dissociation and cohesive energies for mercury clusters have been determined. The mass spectrum of negatively charged Hg clusters is reported. The influence of the transition from van der Waals (n < 13), to covalent (30 < n < 70) to metallic bonding (n > 100) is discussed. A cluster is defined to be metallic , if the ionisation potential behaves like that calculated for a metal sphere. The difference between the measured ionisation potential and that expected for a metallic cluster vanishes rather suddenly around n 100 Hg atoms per cluster. Two possible interpretations are discussed, a rapid decrease of the nearest-neighbour distance and/or the analogue of a Mott transition in a finite system. Electronic correlation effects are strong they make the experimentally observed transitions van der Waals/covalent and covalent/metallic more pronounced than calculated in an independent electron theory. 

F nmr spectra have been reported for tetrafluoro-l,3-dithietane in solution with nematic liquid crystals D2h symmetry is imputed. " Theoretical calculations of the transition energies and intensities of three different tetraalkyl-1,3-dithietanes indicate a need for the inclusion of d orbitals. Theoretical calculations also have been made on a dimer of 1,3-dithietane. The UV spectrum of 2,2,4,4-tetrachloro-1,3-dithietane has been interpreted with the aid of molecular orbital calculations, interaction between the two sulfur atoms is suggested. The photoelectron spectra of tetrafluoro and tetrachloro-l,3-dithietane and 1,3-dithietane itself have been reported. The negative-ion mass spectrum of tetra-fluoro-1,3-dithietane has a base peak corresponding to fluoride ion the base peak of tetra(trifluoromethyl)-l,3-dithietane corresponds to the anion of hexafluoro-thioacetone. The oxidation potential of 1,3-dithietane does not show any unusual transannular interactions in the cation radical. ... 

The differences in potential energy between the various species formed during Cl can also yield odd effects. The protonated molecule formed by ammonia chemical ionisation of acetyl salicylic acid is so energetic that it decomposes losing water, in some sources, whilst the ammoniated cluster ion is stable. Thus the spectrum shows ions at m/z 163 (M+H -H20) and 198 (M+NH4" ), but no ion at the expected mass m/z 181 (M+H ). Similar effects can be seen using APCI and thermospray, both hot sources where thermal energy can be absorbed to generate thermal decomposition of the intact molecule. Electrospray... 

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