Toward a Determination of the Proton-Electron Mass Ratio from the Lamb-Dip Measurement of HD.

Precision spectroscopy of the hydrogen molecule is a test ground of quantum electrodynamics (QED), and it may serve for the determination of fundamental constants. Using a comb-locked cavity ring-down spectrometer, for the first time, we observed the Lamb-dip spectrum of the R(1) line in the overtone of hydrogen deuteride (HD). The line position was determined to be 217 105 182.79±0.03_{stat}±0.08_{syst} MHz (δν/ν=4×10^{-10}), which is the most accurate rovibrational transition ever measured in the ground electronic state of molecular hydrogen. Moreover, from calculations including QED effects up to the order m_{e}α^{6}, we obtained predictions for this R(1) line as well as for the HD dissociation energy, which are less accurate but signaling the importance of the complete treatment of nonadiabatic effects. Provided that the theoretical calculation reaches the same accuracy, the present measurement will lead to a determination of the proton-to-electron mass ratio with a precision of 1.3 parts per billion.

Thermoresponsive poly[tri(ethylene glycol) monoethyl ether methacrylate]-peptide surfaces obtained by radiation grafting-synthesis and characterisation.

This report demonstrates the feasibility of radiation grafting for the preparation of polymer layers functionalised with short peptide ligands which promote cell adhesion. Thermoresponsive poly [tri(ethylene glycol) monoethyl ether methacrylate] (PTEGMA) layers were synthesised on a polypropylene substrate by post-irradiation grafting. A cell adhesion moiety, the CF-IKVAVK peptide modified with a methacrylamide function and a fluorescent label were introduced to the surface during the polymerisation process. The amount of CF-IKVAVK was easily controlled by changing its concentration in the reaction mixture. The changes in the surface composition, morphology, philicity and thickness at each step of the polypropylene functionalisation confirmed that the surface modification procedures were successful. The increase in environmental temperature above the cloud point temperature of PTEGMA caused a decrease in surface philicity. The obtained PTEGMA and PTEGMA-peptide surfaces above TCP were tested as scaffolds for fibroblast sheet culture and temperature induced detachment.

Fundamental vibration of molecular hydrogen.

The fundamental ground tone vibration of H(2), HD, and D(2) is determined to an accuracy of 2×10(-4) cm(-1) from Doppler-free laser spectroscopy in the collisionless environment of a molecular beam. This rotationless vibrational splitting is derived from the combination difference between electronic excitation from the X(1)Σ(g)(+), v=0, and v=1 levels to a common EF(1)Σ(g)(+), v=0 level. Agreement within 1σ between the experimental result and a full ab initio calculation provides a stringent test of quantum electrodynamics in a chemically bound system.

High accuracy ab initio studies of electron-densities for the ground state of Be-like atomic systems.

Benchmark results for electron densities in the ground states of Li(-), Be, C(2+), Ne(6+), and Ar(14+) have been generated from very accurate variational wave functions represented in terms of extensive basis sets of exponentially correlated Gaussian functions. For Ne(6+), and Ar(14+), the upper bounds to the energies improve over previous results known from the literature. For the remaining systems our bounds are from 0.1 to 1.1 µhartree higher than the most accurate ones. We present in graphical and, partially, numerical form results both for the radial electron densities and for the difference radial density distributions (DRD) (defined with respect to the Hartree-Fock radial density) that highlight the impact of correlation effects on electron densities. Next, we have employed these DRD distributions in studies of the performance of several broadly used orbital-based quantum-chemical methods in accounting for correlation effects on the density. Our computed benchmark densities for Be have been also applied for testing the possibility of using the mathematically strict result concerning exact atomic electron densities, obtained by Ahlrichs et al. [Phys. Rev. A 23, 2106 (1981)], for the determination of the reliability range of computed densities in the long-range asymptotic region. The results obtained for Be are encouraging.

Relativistic and quantum electrodynamics effects in the helium pair potential.

The helium pair potential was computed including relativistic and quantum electrodynamics contributions as well as improved accuracy adiabatic ones. Accurate asymptotic expansions were used for large distances R. Error estimates show that the present potential is more accurate than any published to date. The computed dissociation energy and the average R for the (4)He(2) bound state are 1.62+/-0.03 mK and 47.1+/-0.5 A. These values can be compared with the measured ones: 1.1(-0.2)(+0.3) mK and 52+/-4 A [R. E. Grisenti, Phys. Rev. Lett. 85, 2284 (2000)].