33 research outputs found
The correlation-consistent composite approach: Application to the G3/99 test set
Article discussing research on the correlation consistent composite approach (ccCA) and an application to the G3/99 test set
Application of the Correlation Consistent Composite Approach (ccCA) to Third-Row (Ga-Kr) Molecules
Solvent-Controlled Selective Transformation of 2-Bromomethyl-2-methylaziridines to Functionalized Aziridines and Azetidines
Joint Book-Reading Strategies in Working-Class African American and White Mother-Toddler Dyads
Task Variability Effects on the Language Test Performance of Southern Lower Socioeconomic Class African American and Caucasian Five-Year-Olds
A Comparison of Audiometry and Audiometry With Tympanometry to Determine Middle Ear Status in School-Age Children
African American Mothers’ Views of Their Infants’ Language Development and Language-Learning Environment
Ionic Liquid–Vacuum Interfaces Probed by Reactive Atom Scattering: Influence of Alkyl Chain Length and Anion Volume
The liquid-vacuum interfaces of a series of room-temperature ionic liquids (RTILs) containing the 1-alkyl-3-methylimidazolium cation ([Cnmim]) were investigated by reactive-atom scattering (RAS). The length of the alkyl chain (n = 4, 6, 8, and 12) and the anion type (bis(trifluoromethylsulfonyl)imide ([Tf2N]), trifluoromethanesulfonate ([OTf]), and tetrafluoroborate ([BF4])) were varied systematically to determine their effects on the preferential occupancy of the surface by alkyl chains. The experiments employed collisions with gas-phase, ground-state oxygen atoms, O(3P), generating OH and H2O products that revealed the abundance of abstractable H atoms at the liquid surface. Two complementary approaches with different O atom energies and detection methods were employed: we denote these RAS-laser-induced fluorescence (RAS-LIF) and RAS-mass spectrometry (RAS-MS). [Cnmim][BF4] RTILs were studied by both methods, giving consistent trends of strongly increasing alkyl coverage with chain length. Even for the longest alkyl chain, n = 12, the surface is not saturated with alkyl chains, with some fraction still occupied by other groups. RAS-LIF results for RTILs with the three different anions, over the range of alkyl chain lengths, showed that their surfaces can be distinguished clearly. Alkyl surface coverage depends sensitively on the anionic volume, indicating that the packing of ions at the surface is driven largely by steric effects. Molecular dynamics simulations of the liquid surfaces support all the experimental findings, including the rationalization of expected quantitative differences between the RAS-LIF and RAS-MS results.</p