Description: This article discusses the effect of solvent polarity on the fluorescence emission fine structures of coronene derivatives. Abstract: The fluorescence properties of coronene (Co), benzo[a]coronene (BCo), naphtho[2,3-a]coronene (NCo), dibenzo[a,j]coronene (DCo), naphtho[1,2,3,4-ghi]perylene, benzo[pqr]naphtho[8,1,2-bcd]perylene and dibenzo[cd,lm]perylene dissolved in solvents of varying polarity are reported. Measurements indicated that the emission intensities of the four coronene derivatives depended on solvent polarity. The Co, BCo and NCo scales have been defined as the ratio of the fluorescence intensities of bands I and III of the vibronic spectra. Band III of dibenzo[a,j]coronene was not clearly identifiable in all the solvents studied, and the DCo scale was therefore defined as the intensity ratio of band I and IV. Emission intensity ratios of the three perylene derivatives remained nearly constant, irrespective of solvent polarity.

Description: This article discusses the solubility of pyrene in binary solvent mixtures containing dibutyl ether. Experimental solubilities are reported for pyrene in binary solvent mixtures containing dibutyl ether with n-hexane, cyclohexane, n-heptane, methylcyclohexane, n-octane, isooctane, and tert-butylcyclohexane at 26 °C. Results of these measurements, combined with estimates for the excess Gibbs free energies of the binary solvents, are used to test predictive expressions derived from the nearly ideal binary solvent (NIBS) model. Expressions based on a volume fraction average of solute properties in the two pure solvents predict pyrene solubilities to within a maximum deviation of 10% and an overall average deviation of 3.2%.

Description: This report describes the findings of a study conducted on the watersheds of "Lake Lewisville, Lake Ray Roberts, Lake Grapevine and the Elm Fork of the Trinity River between Lake Lewisville and Frazier Dam," which are all part of the upper Trinity drainage basin (p. 31). The study examines the potential benefit of "remote sensing and geographic information systems (GIS) for watershed management" in and around Dallas, Texas (p. i).

Description: This article discusses M-shell x-ray production cross sections for 0.5-2.5-MeV Be+ ions incident upon selected elements from praseodymium to bismuth. M-shell x-ray production cross sections are reported for ₄⁹Be+ ions incident upon thin ₅₉Pr, ₆₀Nd, ₆₃Eu, ₆₆Dy, ₆₇Ho, ₇₂Hf, ₇₄W, ₇₉Au, ₈₂Pb, and ₈₃Bi targets. Incident-beam energies range from 0.5 to 2.5 MeV (55.6-267 keV/u). The results are compared to the predictions of the first-Born-approximation theory and the perturbed-stationary-state theory with energy-loss, Coulomb-deflection, and relativistic corrections (ECPSSR). The first-Born-approximation theory overpredicts the measured cross sections everywhere, especially at high energies, while the ECPSSR theory tends to underpredict them, especially at low energy. This discrepancy between the measurements and the ECPSSR theory may be due in part to multiple-ionization effects which could change the fluorescence yields from the single-hole values used to convert total ionization to x-ray production cross sections in the theoretical calculations.

Description: This article discusses L- and M-shell x-ray production. Abstract: L- and M-shell x-ray production cross sections have been measured for thin solid targets of neodymium, gadolinium, holmium, ytterbium, gold and lead by 25-MeV ₆¹²C(q)+ (q=4,5,6) and by 32-MeV ₈¹⁶O(q)+ (q=5,7,8). The cross sections were determined from measurements made with thin targets (less than 2.25 μg/cm2). For projectiles with one or two K-shell vacancies, the target x-ray production cross sections were found to be enhanced over those for projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) plus electron capture (EC) to the L,M,N,... shells and EC to the K shell of the projectile have been extracted from the data. The results are compared to the predictions of first Born theories, i.e., plane-wave Born approximation for DI and Oppenheimer-Brinkman-Kramers formula of Nikolaev for EC, and to the ECPSSR that accounts for energy loss and Coulomb deflection of the projectile as well as for relativistic and perturbed stationary states of inner-shell electrons.