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Electronic Excited State and Vibrational Dynamics of Water Solution of Cytosine Observed by Time-resolved Transient Absorption Spectroscopy with Sub-10fs Deep Ultraviolet Laser Pules  [cached]
Miyazaki Jun,Kida Yuichiro,Kobayashi Takayoshi.
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134105017
Abstract: Time-resolved transient absorption spectroscopy for water solution of cytosine with sub-10fs deep ultraviolet laser pulse is reported. Ultrafast electronic excited state dynamics and coherent molecular vibrational dynamics are simultaneously observed and their relaxation mechanisms are discussed.
Direct generation of intense extreme ultraviolet supercontinuum with 35 fs, 11 mJ pulses from a femtosecond laser amplifier  [PDF]
Bin Zeng,Wei Chu,Guihua Li,Jinping Yao,Jielei Ni,Haisu Zhang,Ya Cheng,Zhizhan Xu
Physics , 2011, DOI: 10.1103/PhysRevA.85.033839
Abstract: We report on the generation of intense extreme ultraviolet (EUV) supercontinuum with photon energies spanning from 35 eV to 50 eV (i. e., supporting an isolated attosecond pulse with a duration of ~271 as) by loosely focusing 35 fs, 11 mJ pulses from a femtosecond laser amplifier into a 10-mm long gas cell filled with krypton gas. The dramatic change of spectral and temporal properties of the driver pulses after passing through the gas cell indicates that propagation effects play a significant role in promoting the generation of the EUV supercontinuum.
Extreme ultraviolet emission from dense plasmas generated with sub-10-fs laser pulses  [PDF]
J. Osterholz,F. Brandl,M. Cerchez,T. Fischer,D. Hemmers,B. Hidding,A. Pipahl,G. Pretzler,S. J. Rose,O. Willi
Physics , 2008, DOI: 10.1063/1.2988767
Abstract: The extreme ultraviolet (XUV) emission from dense plasmas generated with sub-10-fs laser pulses with varying peak intensities up to 3*10^16 W/cm^2 is investigated for different target materials. K shell spectra are obtained from low Z targets (carbon and boron nitride). In the spectra a series limit for the hydrogen and helium like resonance lines is observed indicating that the plasma is at high density and pressure ionization has removed the higher levels. In addition, L shell spectra from titanium targets were obtained. Basic features of the K and L shell spectra are reproduced with computer simulations. The calculations include hydrodynamic simulation of the plasma expansion and collisional radiative calculations of the XUV emission.
Generation of Continuum Extreme-Ultraviolet Radiation by Carrier-Envelope-Phase-Stabilized 5-fs Laser Pulses

TENG Hao,YUN Chen-Xia,ZHU Jiang-Feng,HAN Hai-Nian,ZHONG Xin,ZHANG Wei,HOU Xun,WEI Zhi-Yi,

中国物理快报 , 2009,
Abstract: Coherent extreme-ultraviolet (XUV) radiation is studied by interaction of carrier-envelope (CE) phase stabilized high energy 5-fs infrared (800\,nm) laser pulses with neon gas at a repetition rate of 1kHz. A broadband continuum XUV spectrum in the cut-off region is demonstrated when the CE phase is shifted to about zero, rather than modulated spectral harmonics when setting of CE phase is nonzero. The results show the generation of isolated attosecond XUV pulses.
Tracing molecular dynamics at the femto-/atto-second boundary through extreme-ultraviolet pump-probe spectroscopy  [PDF]
P. A. Carpeggiani,P. Tzallas,A. Palacios,D. Gray,F. Martín,D. Charalambidis
Physics , 2013,
Abstract: Coherent light pulses of few to hundreds of femtoseconds (fs) duration have prolifically served the field of ultrafast phenomena. While fs pulses address mainly dynamics of nuclear motion in molecules or lattices in the gas, liquid or condensed matter phase, the advent of attosecond pulses has in recent years provided direct experimental access to ultrafast electron dynamics. However, there are processes involving nuclear motion in molecules and in particular coupled electronic and nuclear motion that possess few fs or even sub-fs dynamics. In the present work we have succeeded in addressing simultaneously vibrational and electronic dynamics in molecular Hydrogen. Utilizing a broadband extreme-ultraviolet (XUV) continuum the entire, Frank-Condon allowed spectrum of H2 is coherently excited. Vibrational, electronic and ionization 1fs scale dynamics are subsequently tracked by means of XUV-pump-XUV-probe measurements. These reflect the intrinsic molecular behavior as the XUV probe pulse hardly distorts the molecular potential.
Femtosecond photoelectron and photoion spectrometer with vacuum ultraviolet probe pulses  [PDF]
Markus Koch,Thomas J. A. Wolf,Jakob Grilj,Emily Sistrunk,Markus Gühr
Physics , 2014,
Abstract: We describe a setup to study ultrafast dynamics in gas-phase molecules using time-resolved photoelectron and photoion spectroscopy. The vacuum ultraviolet (VUV) probe pulses are generated via strong field high-order harmonic generation from infrared femtosecond laser pulses. The band pass characteristic in transmission of thin indium (In) metal foil is exploited to isolate the $9^{\text{th}}$ harmonic of the 800 nm fundamental (H9, 14 eV, 89 nm) from all other high harmonics. The $9^{\text{th}}$ harmonic is obtained with high conversion efficiencies and has sufficient photon energy to access the complete set of valence electron levels in most molecules. The setup also allows for direct comparison of VUV single-photon probe with 800 nm multi-photon probe without influencing the delay of excitation and probe pulse or the beam geometry. We use a magnetic bottle spectrometer with high collection efficiency for electrons, serving at the same time as a time of flight spectrometer for ions. Characterization measurements on Xe reveal the spectral width of H9 to be $190\pm60$ meV and a photon flux of $\sim1\cdot10^{7}$ photons/pulse after spectral filtering. As a first application, we investigate the S$_1$ excitation of perylene using time-resolved ion spectra obtained with multi-photon probing and time-resolved electron spectra from VUV single-photon probing. The time resolution extracted from cross-correlation measurements is $65\pm10$ fs for both probing schemes and the pulse duration of H9 is found to be $35\pm8$ fs.
Cascaded Nondegenerate Four-Wave Mixing Technique for High-Power Single-Cycle Pulse Synthesis in the Visible and Ultraviolet Ranges  [PDF]
Rosa Weigand,J. T. Mendonca,Helder M. Crespo
Physics , 2009, DOI: 10.1103/PhysRevA.79.063838
Abstract: We present a new technique to synthesize high-power single-cycle pulses in the visible and ultraviolet ranges by coherent superposition of a multiband octave-spanning spectrum obtained by highly-nondegenerate cascaded four-wave mixing of femtosecond pulses in bulk isotropic nonresonant media. The generation of coherent spectra spanning over two octaves in bandwidth is experimentally demonstrated using a thin fused silica slide. Full characterization of the intervening multicolored fields using frequency-resolved optical gating, where multiple cascaded orders have been measured simultaneously for the first time, supports the possibility of direct synthesis of near-single-cycle 2.2 fs visible-UV pulses without recurring to complex amplitude or phase control, which should enable many applications in science and technology.
Time-resolved four-wave-mixing spectroscopy for inner-valence transitions  [PDF]
Thomas Ding,Christian Ott,Andreas Kaldun,Alexander Bl?ttermann,Kristina Meyer,Veit Stoo?,Marc Rebholz,Paul Birk,Maximilian Hartmann,Andrew Brown,Hugo Van Der Hart,Thomas Pfeifer
Physics , 2015,
Abstract: Non-collinear four-wave mixing (FWM) techniques at near-infrared (NIR), visible, and ultraviolet frequencies have been widely used to map vibrational and electronic couplings, typically in complex molecules. However, correlations between spatially localized inner-valence transitions among different sites of a molecule in the extreme ultraviolet (XUV) spectral range have not been observed yet. As an experimental step towards this goal we perform time-resolved FWM spectroscopy with femtosecond NIR and attosecond XUV pulses. The first two pulses (XUV-NIR) coincide in time and act as coherent excitation fields, while the third pulse (NIR) acts as a probe. As a first application we show how coupling dynamics between odd- and even-parity inner-valence excited states of neon can be revealed using a two-dimensional spectral representation. Experimentally obtained results are found to be in good agreement with ab initio time-dependent R-matrix calculations providing the full description of multi-electron interactions, as well as few-level model simulations. Future applications of this method also include site-specific probing of electronic processes in molecules.
Revealing Correlated Electron-Nuclear Dynamics in Molecules with Energy-Resolved Population Image  [PDF]
Kunlong Liu,Pengfei Lan,Cheng Huang,Qingbin Zhang,Peixiang Lu
Physics , 2014, DOI: 10.1103/PhysRevA.89.053423
Abstract: We explore a new fashion, named energy-resolved population image (EPI), to represent on an equal footing the temporary electronic transition and nuclear motion during laser-molecular interaction. By using the EPI we have intuitively demonstrated the population transfer in vibrational H$_2^+$ exposed to extreme ultraviolet pulses, revealing the energy sharing rule for the correlated electron and nuclei. We further show that the EPI can be extended to uncover the origins of the distinct energy sharing mechanisms in multi-photon and tunneling regimes. The present study has clarified a long-standing issue about the dissociative ionization of H$_2^+$ and paves the way to identify instantaneous molecular dynamics in strong fields.
Near-field diffraction of fs and sub-fs pulses: super-resolutions of NSOM in space and time  [PDF]
S. V. Kukhlevsky,M. Mechler,L. Csapo
Physics , 2003, DOI: 10.1016/j.physleta.2003.10.054
Abstract: The near-field diffraction of fs and sub-fs light pulses by nm-size slit-type apertures and its implication for near-field scanning optical microscopy (NSOM) is analyzed. The amplitude distributions of the diffracted wave-packets having the central wavelengths in the visible spectral region are found by using the Neerhoff and Mur coupled integral equations, which are solved numerically for each Fourier's component of the wave-packet. In the case of fs pulses, the duration and transverse dimensions of the diffracted pulse remain practically the same as that of the input pulse. This demonstrates feasibility of the NSOM in which a fs pulse is used to provide the fs temporal resolution together with nm-scale spatial resolution. In the sub-fs domain, the Fourier spectrum of the transmitted pulse experiences a considerable narrowing that leads to the increase of the pulse duration in a few times. This imposes a limit on the simultaneous resolutions in time and space.
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