Transient Alignment of Distinct l-Doubling Populations via Centrifugal Distortion Precompensation

We experimentally demonstrate a coherent-control scheme for precompensation of centrifugal distortion using shaped femtosecond laser pulses. By imposing a cubic spectral phase on the excitation pulse [Y. Huang et al., Phys. Rev. A 107, 053108 (2023)], rotational revivals that would otherwise become temporally broadened, multicycle, and overlap with neighboring rotational contributions are compressed into near single-cycle structures. An analytic expression derived from molecular rotational constants enables predictive pulse design and is validated experimentally. As a stringent demonstration of this control scheme, we achieve transient alignment of distinct l-doubling populations in CO_{2}. More broadly, the demonstrated control scheme enables the selective preparation of closely spaced molecular components in controlled anisotropic angular distributions, with direct relevance to molecular-frame spectroscopies and advanced coherent control.