No abstract

Multiphoton absorption (MPA) of HF laser radiation has been studied, as a function of pressure (15 Pa to 1.3 kPa) and fluence (2 mJ/cm2 to 75 J/cm2) for the series: water, methanol, methan-d3-ol, ethanol, and 2,2,2-trifluoroethanol. As the group attached to the –OH is made more complex, the quasicontinuum occurs after fewer excitation steps, and under ’’collisionless’’ conditions, the same degree of multiphoton excitation is found to require a lower fluence. For water, at pressures between 73 Pa and 1.3 kPa, the cross sections are considerably lower than those for the other molecules, and MPA requires fluences in excess of ∼75 J/cm2. The remaining molecules divide into two groups, the ’’small’’ molecules (CH3OH and CD3OH) and the ’’large’’ molecules (C2H5OH and CF3CH2OH). For the small molecules at low pressures, the cross sections decrease with increasing fluence, an effect which is thought to be due to anharmonic bottlenecking. As pressure increases, the fluence dependence of the cross sections disappear. For the large molecules, anharmonic bottlenecking appears to be reduced, due to the greater density of states, and cross sections increase with increasing fluence according to the empirical form: σ(E, P)=K′Eb′Pa (where P is pressure, E is fluence and b′, a, and K′ are constants). The facility of HF laser-induced collisionless multiphoton dissociation of the –OH containing molecules is discussed in light of these results.

Partition coefficients in cyclohexane-water were determined for 160 conjugated heteroenoid compounds and were used to calculate n constants for several component groupings of molecules.

No abstract

Except for the benzalmalononitriles, two functional group strctching vibrations occur in the infrared (i.r.) spectra of the b,b-difunctional-styrenes with similar functional groups. For geometrically homogeneous compounds with dissimilar functional groups only one absorption band occurs for each functional group. The two bands for similar functional groups have been ascribed to S-cis-and S-trnrrsconformations of the carbonyl groups with respect to the ethylene and variation in the frequencies of each of these oriented carbonyls to rotation of the functional group or groups out of the plane of the ethylene by steric factors.Frequencies for ethylenic C-H out of plane deformation bands for 8-n~onofunctional styrenes accorded with those already assigned to this vibration. A similar assignment could not be made for the difi~nctional analogues.