Search results for "resolve"

Characterisation of Chlorophyll a and Chlorophyll b Monomers in Various Solvent Environments with Ultrafast Spectroscopy

1998

In photosynthesis the energy from the sun is captured by light harvesting chlorophyll pigments and converted to stable chemical energy, by the photochemical reaction center. Photosynthetic energy transfer in the antenna systems of green plants has previously been studied by ultrafast time resolved spectroscopy. The characteristics of the chlorophyll pigments itself is important to study in order to understand the dynamics on a femtosecond timescale. One way to study the energy transfer is to use transient absorption spectroscopy and follow the increase or decrease in the transient absorption signal with time (1). Another way to study the energy transfer is to monitor the change in dichroism…

Quantitative microscopy of magnetic domains in Fe(100) by core-level x-ray photoelectron spectroscopy

2005

We present an experimental technique for imaging of magnetic domain patterns based on element-specific core-level photoemission using polarized soft-x-ray radiation. It is applied to the measurement of domain patterns at the Fe(100) surface and at the surface of polycrystalline Fe. Different from well established imaging techniques that use a photoemission electron microscope to measure the secondary electron intensity at the Fe absorption threshold, we have investigated the photoemission intensity contrast on the the Fe $2{p}_{3∕2}$ core level using circularly polarized x-ray light. The linear and circular dichroism characteristics of the identical domain pattern are extracted by linear co…

Magnetic Circular Dichroism in Two-Photon Photoemission

2009

We report the observation of magnetic circular dichroism (MCD) in two-photon photoemission (2PPE). The Heusler alloys Ni2MnGa and Co2FeSi were investigated by excitation with femtosecond laser light, showing MCD asymmetries of A=(3.5+/-0.5)x10;{-3} for Ni2MnGa and of A=(2.1+/-1.0)x10;{-3} for Co2FeSi, respectively. A theoretical explanation is provided based on local spin-density calculations for the magnetic dichroic response; the computed 2PPE MCD agrees well with the experiment. The observed 2PPE magnetic contrast represents an interesting alternative for future time-resolved photoemission studies on surface magnetism practicable in the laboratory.

Perturbations of Jordan Blocks

2019

In this chapter we shall study the spectrum of a random perturbation of the large Jordan block A0, introduced in Sect. 2.4: $$\displaystyle A_0=\begin {pmatrix}0 &1 &0 &0 &\ldots &0\\ 0 &0 &1 &0 &\ldots &0\\ 0 &0 &0 &1 &\ldots &0\\ . &. &. &. &\ldots &.\\ 0 &0 &0 &0 &\ldots &1\\ 0 &0 &0 &0 &\ldots &0 \end {pmatrix}: {\mathbf {C}}^N\to {\mathbf {C}}^N. $$ Zworski noticed that for every z ∈ D(0, 1), there are associated exponentially accurate quasimodes when N →∞. Hence the open unit disc is a region of spectral instability. We have spectral stability (a good resolvent estimate) in \(\mathbf {C}\setminus \overline {D(0,1)}\), since ∥A0∥ = 1. σ(A0) = {0}.

El infierno son los otros

2002

Ultrafast Metamorphosis of a Complex Charge Density Wave in Tantalumdiselenite

2016

Using ultrafast electron diffraction, we record the transformation between a nearly-commensurate and an incommensurate charge-density-wave in 1T-TaS2, which takes place orders of magnitude faster than previously observed for commensurate-to-incommensurate transitions.

Valence band photoemission from thin iron films - A comparison of experimental and theoretical results

1998

Abstract In this contribution, we report on photoemission data from thin iron films on W(110) that have been carried out by means of spin-resolved photoelectron spectroscopy as well as Magnetic Circular Dichroism in valence band photoemission at the storage ring BESSY. These techniques give complementary information on the electronic and magnetic properties, such as exchange and spin–orbit splitting. We compare our experimental data to new photoemission calculations, which have been obtained in the framework of a fully relativistic one-step theory for ferromagnetic materials.

Environment assisted photoconversion of luminescent surface defects in SiO 2 nanoparticles

2017

Abstract Time-resolved photoluminescence investigation on SiO 2 nanoparticles was carried out in controlled atmosphere, with the aim to discern the effects induced on the typical blue luminescence band by high power UV Nd:YAG laser photons (4.66 eV) and by some selected molecular species of the air (O 2 , N 2 , CO 2 , H 2 O). These factors ultimately determine both the brightness and photostability of the emitting defect, so as to limit the unique and attracting potentialities offered by this system in many applicative fields. Here it is highlighted that the effects due to photons and molecules, singularly considered, are not additive, the radiation being more dramatic in reducing the emiss…

Application of time-resolved spectroscopy to concentration measurements in gas mixtures

2001

1296-2147; Concentration measurements using femtosecond Raman Induced Polarization Spectroscopy (RIPS) are performed in binary gas mixtures CO2-N2 and CO2-N2O at room temperature. The principle of these measurements is based on the nonlinear rotational time response of each molecular component of the mixture, The general form of this molecular response is a series of periodic transients with a period related to the rotational constant Be The relative strength of the individual responses allows an accurate determination of the concentration. Two techniques are presented using either two pulses (one pump and one probe) or three pulses (two pumps and one probe). (C) 2001 Academie des sciences/…

Anomalous d-like surface resonances on Mo(110) analyzed by time-of-flight momentum microscopy.

2015

The electronic surface states on Mo(110) have been investigated using time-of-flight momentum microscopy with synchrotron radiation (hν=35 eV). This novel angle-resolved photoemission approach yields a simultaneous acquisition of the E-vs-k spectral function in the full surface Brillouin zone and several eV energy interval. (kx,ky,EB)-maps with 3.4 A(-1) diameter reveal a rich structure of d-like surface resonances in the spin-orbit induced partial band gap. Calculations using the one-step model in its density matrix formulation predict an anomalous state with Dirac-like signature and Rashba spin texture crossing the bandgap at Γ¯ and EB=1.2 eV. The experiment shows that the linear dispersi…