  High-harmonic generation is typically thought of as a sub-laser-cycle
process, with the electron's excursion in the continuum lasting a fraction of
the optical cycle. However, it was recently suggested that long-lived Rydberg
states can play a particularly important role in atoms driven by the
combination of the counter-rotating circularly polarized fundamental light
field and its second harmonic. Here we report direct experimental evidence of
long and stable Rydberg trajectories contributing to high-harmonic generation.
We confirm their effect on the harmonic emission via Time-Dependent
Schr{\"o}dinger Equation simulations and track their dynamics inside the laser
pulse using the spin-orbit evolution in the ionic core, utilizing the
spin-orbit Larmor clock. Our observations contrast sharply with the general
view that long-lived Rydberg orbits should generate negligible contribution to
the macroscopic far-field high harmonic response of the medium. Indeed, we show
how and why radiation from such states can lead to well collimated macroscopic
signal in the far field.
