Orientation-dependent production of electron spirals from multi-orbital heteronuclear diatomic molecules*

When an atom is photoionized by time-delayed, oppositely circularly polarized laser broadband pulses, the resulting photoelectron momentum distribution (PMD) reveals electron spirals in the polarization plane encoding the symmetries of atomic orbitals [1,2,3]. In this work, we extend this approach with the aim of probing the orbital symmetries of heteronuclear, multi-orbital aligned molecules [4]. The focus of studies [5,6] were on homonuclear single-orbital molecules using single-color [5] or two-color [6] fields. For laser pulses with spectral width larger than the characteristic energy gap between inner and outer orbitals, photoionization from all these orbitals becomes possible as shown here for heteronuclear molecules. Indeed, although the broad bandwidth of the laser pulses generates multiplexed molecular-frame PMDs that obscure orbital-specific features, we show that the molecular orientation relative to the light propagation direction enables selective control of ionization channels. This provides an effective strategy for identifying asymmetries in the highest-occupied molecular orbital, manifested as asymmetric molecular spirals induced by single-color time-delayed pulses. These results demonstrate the potential of polarization-tailored attosecond pulse sequences as a powerful spectroscopic tool for unveiling molecular orbital symmetries.

[1]. J. M. Ngoko Djiokap, S. X. Hu, L. B. Madsen, N. L. Manakov, A. V. Meremianin, and A. F. Starace  Phys. Rev. Lett. 115, 113004 (2015)

[2] D. Pengel et al., Phys. Rev. Lett. 118, 053003 (2017).

[3] D. Pengel, S. Kerbstadt, L. Englert, T. Bayer, and M. Wollenhaupt, Phys. Rev. A 96, 043426 (2017).

[4] H. B. Ambalampitiya and J. M. Ngoko Djiokap, Comm. Phys. 7, 359 (2024)

[5] K.-J. Yuan, S. Chelkowski, A. D. Bandrauk, Phys. Rev. A 93, 053425 (2016).

[6] R. R. Wang et al., J. Opt. Soc. Am. B 40, 1749–1755 (2023).