The role of dipole-forbidden autoionizing resonances in non-resonant one-color two-photon single ionization of N\(_2\)

• Published in: arXiv.org
• Main Authors: Larsen, Kirk A, Bello, Roger Y, Lucchese, Robert R, Rescigno, Thomas N, McCurdy, C William, Slaughter, Daniel S, Weber, Thorsten
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 29.12.2020
• Subjects: Color; Dipoles; Harmonic generations; Ionization; Kinetic energy; Photoelectrons; Photoionization; Photons
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2009.08669

We present an experimental and theoretical energy- and angle-resolved study on the photoionization dynamics of non-resonant one-color two-photon single valence ionization of neutral N\(_2\) molecules. Using 9.3 eV photons produced via high harmonic generation and a 3-D momentum imaging spectrometer, we detect the photoelectrons and ions produced from one-color two-photon ionization in coincidence. Photoionization of N\(_2\) populates the X \(^2\Sigma^+_g\), A \(^2\Pi_u\), and B \(^2\Sigma^+_u\) ionic states of N\(_2^+\), where the photoelectron angular distributions associated with the X \(^2\Sigma^+_g\) and A \(^2\Pi_u\) states both vary with changes in photoelectron kinetic energy of only a few hundred meV. We attribute the rapid evolution in the photoelectron angular distributions to the excitation and decay of dipole-forbidden autoionizing resonances that belong to series of different symmetries, all of which are members of the Hopfield series, and compete with the direct two-photon single ionization.