The role of dipole-forbidden autoionizing resonances in non-resonant one-color two-photon single ionization of N${}_2$

Abstract

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.

12 pages, 9 figures, 2 tables

References in corpus (2)

• Distinguishing resonance symmetries with energy-resolved photoion angular distributions from ion-pair formation in O${}_2$ following two-photon absorption of a 9.3 eV femtosecond pulse
• Angle-resolved non-resonant two-photon single ionization of argon using 9.3 eV photons produced via high harmonic generation

Cited by in corpus (1)

• Multi-photon above threshold ionization of multi-electron atoms and molecules using the R-matrix approach