Dynamical phase shift in x ray absorption and ionization spectra by two delayed x ray laser fields

We study theoretically x ray absorption and ionization spectra of an atom or molecule by two coherent x ray pulses that show a relative phase shift resulting in a time delay of the pulse envelopes. We demonstrate that the phase modulation of the spectra is shifted with respect to the phase oscillation comb of the x ray double pulse. The reason for this shift is the dynamics of the process defined by the interplay of the delay time, the pulse width, the detuning, and the lifetime of the core excited stat

High resolution x ray spectra of carbon monoxide reveal ultrafast dynamics induced by long UV pulse

In theoretical simulations of a UV x ray pump probe UVX PP setup, we show that frequency detuning of the pump UV pulse acts as a camera shutter by regulating the duration of the UVX PP process. This two photon absorption with long overlapping UV and x ray pulses, allowing for high spectral resolution, thereby provides information about ultrafast dynamics of the nuclear wave packet without the requirement of ultrashort pulses and controlled delay times. In a case study of carbon monoxide, the calculated UVX PP spectra of the O1s amp; 8722;12 amp; 960;1 and C1s amp; 8722;12 amp; 960;1 core excited states show different vibrational profiles. The interference of intermediate vibrational states reveals details of nuclear dynamics in the UVX PP process related to a variable duration time controlled by the UV detuning. Both O1s amp; 8722;12 amp; 960;1 and C1s amp; 8722;12 amp; 960;1 pump probe channels display a splitting of the spectral profile, which however is associated with different physical mechanisms. At the O1s amp; 8722;12 amp; 960;1 resonance, the observed dispersive and non dispersive spectral bands intersect and result in destructive interferenc

Non-quasiparticle states in the core level spectra of ferromagnetic semiconductors and half-metallic ferromagnets

The Green's functions that determine x-ray spectra are calculated in the s-d exchange model of a saturated conducting ferromagnet in the presence of the core hole. A possibility to observe non-quasiparticle (NQP) states in the core level (x-ray absorption, emission and photoelectron) spectroscopy is demonstrated. It is shown that NQP contributions to resonant x-ray scattering spectra can be considerably enhanced by core hole effects in comparison with those to the density of states.Comment: 13 pages, 7 figures, final versio

Time resolved study of recoil induced rotation by X ray pump X ray probe spectroscopy

Modern stationary X ray spectroscopy is unable to resolve rotational structure. In the present paper, we propose to use time resolved two color X ray pump probe spectroscopy with picosecond resolution for real time monitoring of the rotational dynamics induced by the recoil effect. The proposed technique consists of two steps. The first short pump X ray pulse ionizes the valence electron, which transfers angular momentum to the molecule. The second time delayed short probe X ray pulse resonantly excites a 1s electron to the created valence hole. Due to the recoil induced angular momentum the molecule rotates and changes the orientation of transition dipole moment of core excitation with respect to the transition dipole moment of the valence ionization, which results in a temporal modulation of the probe X ray absorption as a function of the delay time between the pulses. We developed an accurate theory of the X ray pump probe spectroscopy of the recoil induced rotation and study how the energy of the photoelectron and thermal dephasing affect the structure of the time dependent X ray absorption using the CO molecule as a case study. We also discuss the feasibility of experimental observation of our theoretical findings, opening new perspectives in studies of molecular rotational dynamic

Resonant X-ray emission spectroscopy reveals d–d ligand-field states involved in the self-assembly of a square-planar platinum complex

Resonant X-ray Emission Spectroscopy (RXES) is used to characterize the ligand field states of the prototypic self-assembled square-planar complex, [Pt(tpy)Cl]Cl (tpy=2,2′:6′,2′′-terpyridine), and determine the effect of weak metal-metal and π-π interactions on their energy. © 2012 the Owner Societies

One dimensional cuts through multidimensional potential energy surfaces by tunable x rays

The concept of the potential energy surface PES and directional reaction coordinates is the backbone of our description of chemical reaction mechanisms. Although the eigenenergies of the nuclear Hamiltonian uniquely link a PES to its spectrum, this information is in general experimentally inaccessible in large polyatomic systems. This is due to near degenerate rovibrational levels across the parameter space of all degrees of freedom, which effectively forms a pseudospectrum given by the centers of gravity of groups of close lying vibrational levels. We show here that resonant inelastic x ray scattering RIXS constitutes an ideal probe for revealing one dimensional cuts through the ground state PES of molecular systems, even far away from the equilibrium geometry, where the independent mode picture is broken. We strictly link the center of gravity of close lying vibrational peaks in RIXS to a pseudospectrum which is shown to coincide with the eigenvalues of an effective one dimensional Hamiltonian along the propagation coordinate of the core excited wave packet. This concept, combined with directional and site selectivity of the core excited states, allows us to experimentally extract cuts through the ground state PES along three complementary directions for the showcase H2O molecul

Selective gating to vibrational modes through resonant X ray scattering

The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X ray scattering RIXS study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X ray excitation to different core excited potential energy surfaces PESs will act as spatial gates to selectively probe the particular ground state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra high resolution RIXS measurements for gas phase water with state of the art simulation

A study of the water molecule using frequency control over nuclear dynamics in resonant X ray scattering

In this combined theoretical and experimental study we report a full analysis of the resonant inelastic X ray scattering RIXS spectra of H 2O, D 2O and HDO. We demonstrate that electronically elastic RIXS has an inherent capability to map the potential energy surface and to perform vibrational analysis of the electronic ground state in multimode systems. We show that the control and selection of vibrational excitation can be performed by tuning the X ray frequency across core excited molecular bands and that this is clearly reflected in the RIXS spectra. Using high level ab initio electronic structure and quantum nuclear wave packet calculations together with high resolution RIXS measurements, we discuss in detail the mode coupling, mode localization and anharmonicity in the studied system

Ultrafast dissociation features in RIXS spectra of the water molecule

In this combined theoretical and experimental study we report on an analysis of the resonant inelastic X ray scattering RIXS spectra of gas phase water via the lowest dissociative core excited state 1s amp; 8722;1O4a11 amp; 12297;. We focus on the spectral feature near the dissociation limit of the electronic ground state. We show that the narrow atomic like peak consists of the overlapping contribution from the RIXS channels back to the ground state and to the first valence excited state 1b amp; 8722;114a11 amp; 12297; of the molecule. The spectral feature has signatures of ultrafast dissociation UFD in the core excited state, as we show by means of ab initio calculations and time dependent nuclear wave packet simulations. We show that the electronically elastic RIXS channel gives substantial contribution to the atomic like resonance due to the strong bond length dependence of the magnitude and orientation of the transition dipole moment. By studying the RIXS for an excitation energy scan over the core excited state resonance, we can understand and single out the molecular and atomic like contributions in the decay to the lowest valence excited state. Our study is complemented by a theoretical discussion of RIXS in the case of isotopically substituted water HDO and D2O where the nuclear dynamics is significantly affected by the heavier fragments mas

Dynamics of resonant x ray and Auger scattering

Anoverviewof both experimental and theoretical results in the field of resonant scattering of tunable soft and hard x ray radiation is presented, with a main focus on the closely related processes of resonant inelastic x ray scattering RIXS and resonant Auger scattering RAS . The review starts with an overviewof fundamental dynamical aspects of RIXSillustrated for different systems.Adetailed analysis of case studies with increasing complexity, considering both gas phase and condensed matter liquids and solids applications, is given. In the review, the most important achievements in investigations of coupled electron nuclear dynamics and structural aspects in studies of liquids and solids over the last two decades are outlined. To give a perspective on the insights from RIXS and RAS, the x ray results are discussed against the background of complementary experimental techniques like vibrational infrared absorption and Raman spectroscopy, as well as small angle x ray and neutron scattering. Finally, recent achievements in time resolved studies based on x ray free electron lasers are describe