Micromechanical photothermal spectroscopy of trace gases using functionalized polymers

We demonstrate a novel method to spectroscopically detect and identify trace gases. Micromechanical photothermal spectroscopy (MPS) with functionalized sorbent materials provides trace gas spectra in an optical interaction length of only a few micrometers. We use microcavity interferometry to read out displacements as low as 25 fm/√Hz, heating as low as 200 pW/√Hz, and analyte concentrations as low as 65 parts-per-billion for the nerve agent simulant DMMP. MPS integrated with functional materials represents an important new tool in chip-scale optical sensing.     

The role of the pion cloud in the interpretation of the valence light-cone wavefunction of the nucleon

The pion cloud renormalises the light-cone wavefunction of the nucleon which is measured in hard, exclusive photon-nucleon reactions. We discuss the leading twist contributions to high-energy exclusive reactions taking into account both the pion cloud and perturbative QCD physics. The nucleon’s electromagnetic form-factor at high Q² is proportional to the bare nucleon probability Z and the cross-sections for hard (real at large angle or deeply virtual) Compton scattering are proportional to Z². Our present knowledge of the pion-nucleon system is consistent with Z = 0.7 ± 0.2. If we apply just perturbative QCD to extract a light-cone wavefunction directly from these hard exclusive cross-sections, then the light-cone wavefunction that we extract measures the three valence quarks partially screened by the pion cloud of the nucleon. We discuss how this pion cloud renormalisation effect might be understood at the quark level in terms of the (in-)stability of the perturbative Dirac vacuum in low energy QCD.     

Longitudinal broadening of quenched jets in turbulent color fields

The nearside distribution of particles at intermediate transverse momentum, associated with a high momentum trigger hadron produced in a high energy heavy-ion collision, is broadened in rapidity compared with the jet cone. This broadened distribution is thought to contain the energy lost by the progenitor parton of the trigger hadron. We show that the broadening can be explained as the final-state deflection of the gluons radiated from the hard parton inside the medium by soft, transversely oriented, turbulent color fields that arise in the presence of plasma instabilities. The magnitude of the effect is found to grow with medium size and density and diminish with increasing energy of the associated hadron.     

Cr∶Nd∶GSGG晶体1.061 μm受激发射截面随温度变化特性研究

测量了Cr∶Nd∶GSGG晶体从 - 70℃到 +80℃温度下的荧光发射光谱和荧光寿命 ,计算了该晶体在不同温度下 1 .0 61 μm受激发射截面 ,获得在此温度变化范围内受激发射截面随温度的线性变化关系     

Current-driven resonances in magnetic multilayers

We describe complex variations in resistance of a Co/Cu multilayer, generated by injection of an adjustable dc current density ( approximately 10(9) A/cm(2)) via a point contact. We attribute these variations to coupling of current-induced spin waves to lattice vibrations, leading especially to current-driven resonant excitations of phonons. We propose a simple model to explain the observed structured behavior of the variations as a function of the applied current and magnetic field.     

Superinelastic electron transfer: electron trapping in H2O ice via the N-2((2)Pi(g)) resonance

We present measurements on the trapping of 0-3 eV electrons in H2O ice films covered with a submonolayer of N2 molecules. At the energy of the N-2((2)Pi(g)) shape resonance, the absolute cross section for electron trapping in ice is approximately 5.5 x 10(-16) cm(2), similar to that for vibrational excitations of gaseous N2 via the resonance. This result, indicating that nearly all electrons from autoionization of N-2((2)Pi(g)) are transferred to electron traps in ice, is explained by superinelastic electron transfer from N-2((2)Pi(g)) into preexisting traps in polar ice, leaving N2 in high vibrational excited states.