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We study population distributions and lasing actions of N_2^+ driven by femtosecond lasers with various wavelengths, and uncover an efficient ionic excitation mechanism induced by synchronized ionization and multiphoton resonance. Our…

Ultraintense pulses from X-ray free-electron lasers can drive, within femtoseconds, multiple processes in the inner shells of atoms and molecules in all phases of matter. The ensuing complex ionization pathways of outer-shell electrons from…

Stellar population models produce radiation fields that ionize oxygen up to O+2, defining the limit of standard HII region models (<54.9 eV). Yet, some extreme emission line galaxies, or EELGs, have surprisingly strong emission originating…

Astrophysics of Galaxies · Physics 2021-12-08 Danielle A. Berg , John Chisholm , Dawn K. Erb , Evan D. Skillman , Richard W. Pogge , Grace M. Olivier

The second-order properties of the training loss have a massive impact on the optimization dynamics of deep learning models. Fort & Scherlis (2019) discovered that a large excess of positive curvature and local convexity of the loss Hessian…

Machine Learning · Computer Science 2024-08-15 Artem Vysogorets , Anna Dawid , Julia Kempe

A new simulation box setup is introduced for the precise description of the wavepacket evolution of two electronic systems in intense laser pulses. In this box, the regions of the hydrogen molecule H$_{2} $, and singly and doubly ionized…

Atomic Physics · Physics 2016-03-03 Mohsen Vafaee , Firoozeh Sami , Babak Shokri , Behnaz Buzari , Hassan Sabzyan

The interaction of high intensity laser radiation with mass-limited target exhibits significant enhancement of the ion acceleration when the target is surrounded by an underdense plasma corona, as seen in numerical simulations. The…

Plasma Physics · Physics 2016-06-22 K. V. Lezhnin , F. F. Kamenets , T. Zh. Esirkepov , S. V. Bulanov , O. Klimo , S. Weber , G. Korn

Despite inherently complex multiphoton dynamics, our observations show that Ba double ionization with an infrared laser (8800-8920 cm^{-1}) resembles a single-photon process; namely, its probability is proportional to the laser intensity.…

Atomic Physics · Physics 2013-08-13 I. I. Bondar , V. V. Suran , D. I. Bondar

Molecular hydrogen ions are of metrological relevance due to the possibility of precise theoretical evaluation of their spectrum and of external-field-induced shifts. We report the results of the calculations of the rate of laser-induced…

Atomic Physics · Physics 2018-03-21 Vladimir I. Korobov , Petar Danev , Dimitar Bakalov , Stephan Schiller

We numerically study models of $\mathrm{H}_2$ and $\mathrm{LiH}$ molecules, aligned collinearly with the linear polarization of the external field, to elucidate the possible role of correlation in the enhanced-ionization phenomena.…

Atomic Physics · Physics 2016-01-06 S. Chattopadhyay , S. Bauch , L. B. Madsen

The fixed-nuclei full dimensional time-dependent Schr \"odinger equation is directly solved for H$_2^+$ in the linearly polarized laser field of $I \sim 1.0 \times 10^{14}$W cm$^{-2}$ and $\lambda \sim 1064 $nm Instantaneous ionization rate…

Atomic Physics · Physics 2007-05-23 Mohsen Vafaee , Hassan Sabzyan , Zahra Vafaee , Ali Katanforoush

We examine the effect of laser focusing on the potential of a recently discussed scheme [M.F. Ciappina {\em et al}, Phys. Rev. A 99, 043405 (2019); Las. Phys. Lett. 17, 025301 (2020)] for in situ determination of ultra-high intensities of…

Atomic Physics · Physics 2020-02-27 M. F. Ciappina , E. E. Peganov , S. V. Popruzhenko

The region of the second ionization of helium in the Sun is a narrow layer near the surface. Ionization induces a local change of the adiabatic exponent $\Gamma_1$, which produces a characteristic signature in the frequencies of p-modes. By…

Astrophysics · Physics 2007-05-23 M. J. P. F. G. Monteiro , M. J. Thompson

Intense-field ionization of the hydrogen molecular ion by linearly-polarized light is modelled by direct solution of the fixed-nuclei time-dependent Schr\"odinger equation and compared with recent experiments. Parallel transitions are…

Computational Physics · Physics 2009-11-10 Liang-You Peng , Daniel Dundas , J F McCann , K T Taylor , I D Williams

Double ionization of diatomic molecules by short linearly polarized laser pulses is analyzed. We consider the final stage of the ionization process, that is the decay of a highly excited two electron molecule, which is formed after…

Atomic Physics · Physics 2016-09-08 Jakub S. Prauzner-Bechcicki , Krzysztof Sacha , Bruno Eckhardt , Jakub Zakrzewski

We investigated electron emissions in strong field enhanced ionization of asymmetric diatomic molecules by quantum calculations. It is demonstrated that the widely-used intuitive physical pic- ture, i.e., electron wave packet direct…

Atomic Physics · Physics 2015-06-18 Cheng Huang , Pengfei Lan , Yueming Zhou , Qingbin Zhang , Kunlong Liu , Peixiang Lu

We theoretically investigate the mechanism of enhanced ionization in two-electron molecules by analyzing Bohmian trajectories for a one-dimensional H2 in an intense laser field. We identify both types of ionizing trajectories corresponding…

Quantum Physics · Physics 2015-06-17 Ryohto Sawada , Takeshi Sato , Kenichi L. Ishikawa

Using a three-dimensional quasiclassical technique we explore molecular double ionization by a linearly polarized, infrared (800 nm) and ultrashort (6 fs) laser pulse. We first focus on intensities corresponding to the tunneling regime and…

Atomic Physics · Physics 2015-05-14 A. Emmanouilidou , A. Staudte

We study non-classical pathways and quantum interference in enhanced ionisation of diatomic molecules in strong laser fields using machine learning techniques. Quantum interference provides a bridge, which facilitates intramolecular…

A detailed theoretical investigation of rare gas atom clusters under intense short laser pulses reveals that the mechanism of energy absorption is akin to {\it enhanced ionization} first discovered for diatomic molecules. The phenomenon is…

Atomic and Molecular Clusters · Physics 2009-11-07 Christian Siedschlag , Jan-Michael Rost

We report on a kinematically complete experiment on strong field double ionization of helium using laser pulses with a wavelength of 394\,nm and intensities of $3.5-5.7\times10^{14}\,W/cm^2$. Our experiment reaches the most complete level…