Allylpalladium umpolung in the three-component coupling synthesis of homoallylic amines

[Structure: see text] Homoallylic amines and alpha-amino esters were prepared via a Pd(II)-catalyzed coupling of boronic acids and 1,2-nonadiene with ethyl iminoacetate or aliphatic, aromatic, and heteroaromatic imines. The allylpalladium umpolung was induced by a Pd(OAc)2 catalyst with commercial phosphine ligands.     

Inelastic phonon interactions at solid–graphite interfaces

The presented model predicts thermal boundary conductance at interfaces where one material comprising the junction is characterized by high elastic anisotropy. In contrast to previous approaches, the current methodology accounts for contributions from inelastic scattering through consideration of multiple-phonon interactions. Inelastic contributions become significant as the temperature, as well as the degree of acoustic mismatch between the materials, increases. Inclusion of the inelastic interactions is necessary for a variety of interfacial systems including the metal–graphite boundary examined here. Improvement is shown over existing approaches that address only elastic scattering as both three- and four-phonon interactions significantly augment the transport.     

Muon spin relaxation as a probe of molecular dynamics of organometallic compounds

LF‐Muon Spin Relaxation data are reported for the organometallic compounds Pb(C₆H₅)₄, (C₆H₆)Cr(CO)₃ and (C₅H₅)₂Ru. In each case the change in relaxation rate with temperature shows a peak analogous to the T_1 minimum in NMR. The activation parameters were calculated, and the mechanism of muon spin relaxation in the case of (C₆H₆)Cr(CO)₃ is shown to be the reorientation motion of the benzene ring. This revised version was published online in August 2006 with corrections to the Cover Date.     

Laser and Fourier transform emission spectroscopy of TaCl

The emission spectrum of TaCl has been recorded at high resolution in the 3000-35 000 cm⁻¹ region using a Fourier transform spectrometer. The bands were observed by microwave excitation of a mixture of TaCl₅ vapor and 3.0 Torr of He. Several TaCl bands have also been recorded using the laser ablation/molecular beam source at the University of New Brunswick. A rotational analysis of a number of bands has been obtained and the majority of the stronger bands have been classified into three groups with different lower state spectroscopic constants. The three lower states have been identified as having Ω″ = 0⁺, Ω″ = 2, and (tentatively) Ω″ = 3. The Ω″ = 0⁺ and Ω″ = 2 states are very close in energy and one of these two states is the ground state of TaCl.     

Communication: imaging wavefunctions in dissociative photoionization

The dissociative ionization dynamics of excited electronic states of the xenon dimer, Xe(2), have been studied using velocity map ion imaging (VMI). A one-colour, (2+1) resonant excitation scheme was employed to first excite and then ionize selected vibrational levels of the Xe(2) 6p (2)[(1)∕(2)](0) 0(g)(+) Rydberg state. Cationic fragments were then detected by the VMI. The data provide an outstanding example of the reflection principle in photodissociation with the full nodal structure of the Rydberg state wavefunctions clearly observed in the final Xe(+) kinetic energy distributions without the need for scanning the excitation energy. Fitting of the observed distributions provides detailed and precise information on the form of the Xe(2)(+) I((1)/(2)g) potential energy curve involved which is in excellent agreement with the results of photoelectron imaging studies [Shubert and Pratt, J. Chem. Phys. 134, 044315 (2011)]. Furthermore, the anisotropy of the product angular distributions yields information on the evolution of the electronic character of the ionic state with internuclear separation, R. The combination of the nature of dissociative ionization and the extent of the bound state wavefunctions provide information over an unusually wide range of internuclear separation R (ΔR > 0.75 ?). This would normally require scanning over a considerable energy region but is obtained in these studies at a fixed excitation energy.     

Phase diagram and structural diversity of the densest binary sphere packings

The densest binary sphere packings have historically been very difficult to determine. The only rigorously known packings in the α-x plane of sphere radius ratio α and relative concentration x are at the Kepler limit α=1, where packings are monodisperse. Utilizing an implementation of the Torquato-Jiao sphere-packing algorithm [S. Torquato and Y. Jiao, Phys. Rev. E 82, 061302 (2010)], we present the most comprehensive determination to date of the phase diagram in (α,x) for the densest binary sphere packings. Unexpectedly, we find many distinct new densest packings.     

Extreme conditions during multibubble cavitation: Sonoluminescence as a spectroscopic probe

We review recent work on the use of sonoluminescence (SL) to probe spectroscopically the conditions created during cavitation, both in clouds of collapsing bubbles (multibubble sonoluminescence, (MBSL)) and in single bubble events. The effective MBSL temperature can be controlled by the vapor pressure of the liquid or the thermal conductivity of the dissolved gas over a range from ～1600 to ～9000K. The effective pressure during MBSL is ～300bar, based on atomic line shifts. Given nanosecond emission times, this means that cooling rates are >10(12)K/s. In sulfuric and phosphoric acid, the low volatility and high solubility of any sonolysis products make bubble collapse more efficient and evidence for an optically opaque plasma core is found.