Photoelectron angular distributions in infrared one-photon and two-photon ionization of FEL-pumped Rydberg states of helium

The photoelectron angular distributions (PADs) have been investigated for infrared (IR) ionization of He atoms excited to Rydberg states by extreme ultraviolet free-electron laser pulses. The experiment was carried out with two pulses which do not overlap in time. Depending on the intensity of the IR pulses, one IR photon ionization or additionally two-photon above-threshold ionization is observed. For low IR intensity, the PAD is well described by a contribution of s and d partial waves in accordance with early experiments. At high IR intensity, the PAD for two IR photon ionization clearly shows the contribution of higher partial waves. The experimental data are compared with the results of theoretical calculations based on solving the time-dependent Schrödinger equation.

[1]  Tetsuya Ishikawa,et al.  Compact XFEL and AMO sciences: SACLA and SCSS , 2013 .

[2]  K. Ishikawa,et al.  Photoelectron Angular Distribution and Phase in Two-Photon Single Ionization of H and He by a Femtosecond and Attosecond Extreme-Ultraviolet Pulse , 2013 .

[3]  P. O’Keeffe,et al.  Near-threshold photoelectron angular distributions from two-photon resonant photoionization of He , 2013 .

[4]  N. Kabachnik,et al.  Effect of partial temporal coherence of XUV pulses in IR-laser-assisted photoionization , 2012 .

[5]  H. Hotop,et al.  Photoionization dynamics of excited Ne, Ar, Kr and Xe atoms near threshold , 2012 .

[6]  K. Ishikawa,et al.  Competition of resonant and nonresonant paths in resonance-enhanced two-photon single ionization of He by an ultrashort extreme-ultraviolet pulse , 2011, 2012 Conference on Lasers and Electro-Optics (CLEO).

[7]  T. Ishikawa,et al.  Second-order autocorrelation of XUV FEL pulses via time resolved two-photon single ionization of He. , 2011, Optics express.

[8]  T. Ishikawa,et al.  Performance of focusing mirror device in EUV beamline of SPring-8 Compact SASE Source (SCSS) , 2011 .

[9]  T. Ishikawa,et al.  Determination of the absolute two-photon ionization cross section of He by an XUV free electron laser , 2011 .

[10]  S. Leone,et al.  Energy-dependent photoelectron angular distributions of two-color two-photon above threshold ionization of atomic helium , 2011 .

[11]  T. Ishikawa,et al.  Multiphoton double ionization of Ar in intense extreme ultraviolet laser fields studied by shot-by-shot photoelectron spectroscopy. , 2010, Physical review letters.

[12]  S. Leone,et al.  Time-resolved photoelectron angular distributions and cross-section ratios of two-colour two-photon above threshold ionization of helium , 2010 .

[13]  S. Leone,et al.  Continuum phase shifts and partial cross sections for photoionization from excited states of atomic helium measured by high-order harmonic optical pump-probe velocity map imaging , 2009 .

[14]  S. I. Strakhova,et al.  Polarization control in two-color above-threshold ionization of atomic helium. , 2008, Physical review letters.

[15]  Chao Zhang,et al.  A compact free-electron laser for generating coherent radiation in the extreme ultraviolet region , 2008 .

[16]  N. M. Kabachnik,et al.  Theoretical description of atomic photoionization by attosecond XUV pulses in a strong laser field: the case of p-shell ionization , 2007 .

[17]  N. Kabachnik,et al.  Theoretical description of atomic photoionization by an attosecond XUV pulse in a strong laser field: effects of rescattering and orbital polarization , 2007 .

[18]  E. Plönjes,et al.  Two-color photoionization in xuv free-electron and visible laser fields , 2006 .

[19]  P. Agostini,et al.  Multicolour above-threshold ionization of helium: quantum interference effects in angular distributions , 2005 .

[20]  Katsumi Midorikawa,et al.  Multiphoton ionization of He by using intense high-order harmonics in the soft-x-ray region , 2005 .

[21]  T. Kanai,et al.  Nonlinear optics in the extreme ultraviolet , 2004, Nature.

[22]  T. Kanai,et al.  Observation of two-photon above-threshold ionization of rare gases by XUV harmonic photons , 2004, InternationalQuantum Electronics Conference, 2004. (IQEC)..

[23]  M. Vrakking.  An iterative procedure for the inversion of two-dimensional ion/photoelectron imaging experiments , 2001 .

[24]  L. Nikolopoulos,et al.  Multichannel theory of two-photon single and double ionization of helium , 2001 .

[25]  Rzaewski,et al.  Angular distribution of photoelectrons in the above-threshold ionization of atomic hydrogen. , 1988, Physical review. A, General physics.

[26]  K. Welge,et al.  “Above-threshold-ionization” of atomic hydrogen: Angular distribution of photoelectrons , 1987 .