Electronic State Population Dynamics upon Ultrafast Strong Field Ionization and Fragmentation of Molecular Nitrogen

Abstract

Air-lasing from single ionized N${}_2^{+}$ molecules induced by laser filamentation in air has been intensively investigated and the mechanisms responsible for lasing are currently highly debated. We use ultrafast nitrogen K-edge spectroscopy to follow the strong field ionization and fragmentation dynamics of N${}_2$ upon interaction with an ultrashort 800 nm laser pulse. Using probe pulses generated by extreme high-order harmonic generation, we observe transitions indicative of the formation of the electronic ground X${}^2{\Sigma }_g^{+}$, first excited A${}^2{\Pi }_u$ and second excited B${}^2{\Sigma }_u^{+}$ states of N${}_2^{+}$ on femtosecond time scales, from which we can quantitatively determine the time-dependent electronic state population distribution dynamics of N${}_2^{+}$. Our results show a remarkably low population of the A${}^2{\Pi }_u$ state, and nearly equal populations of the X${}^2{\Sigma }_g^{+}$ and B${}^2{\Sigma }_u^{+}$ states. In addition, we observe fragmentation of N${}_2^{+}$ into N and N${}^{+}$ on a time scale of several tens of picoseconds that we assign to significant collisional dynamics in the plasma, resulting in dissociative excitation of N${}_2^{+}$.

References in corpus (10)

• Lorentz meets Fano spectral line shapes: A universal phase and its laser control
• High-brightness switchable multi-wavelength remote laser in air
• Population Redistribution among Multiple Electronic States of Molecular Nitrogen Ions in Strong Laser Fields
• Recollision induced superradiance of ionized nitrogen molecules
• New determination of structure parameters in strong field tunneling ionization theory of molecules
• Self-seeded lasing in ionized air pumped by 800 nm femtosecond laser pulses
• Molecular movie of ultrafast coherent rotational dynamics
• Rotational Quantum Beat Lasing Without Inversion
• Self-induced white-light seeding laser in a femtosecond laser filament
• N${}_2^{+}$ Lasing: Gain and Absorption in the Presence of Rotational Coherence

Cited by in corpus (5)

• Coherence from multiorbital tunneling ionization of molecules
• Controlling the polarization of nitrogen ion lasing
• Electronic-vibrational dynamics and coherence in x-ray transient absorption of N2+ induced by strong-field ionization
• Revisiting self-seeding mechanism by generating vector ultraviolet N${}_2^{+}$ lasing
• Nonadiabatic theory for subcycle ionic dynamics in multielectron tunneling ionization