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Updated: May 3, 2026
10:52
Direct Imaging of Laser-driven Ultrafast Molecular Rotation
Published on: February 4, 2017
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Threshold alignment reversal and circularly polarized fluorescence in rotationally resolved H2
J W Maseberg1, K Bartschat2, T J Gay3
1Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0299, USA and Department of Physics, Fort Hays State University, Hays, Kansas 67601-4099, USA.
Physical Review Letters
|February 4, 2014
Summary
Spin-polarized electron impact on H2 and D2 molecules reveals dynamic production of specific molecular states. Measurements show nonzero circular polarization, indicating molecular state orientation, with deviations suggesting symmetry perturbations.
Area of Science:
- Atomic and Molecular Physics
- Quantum Mechanics
- Chemical Physics
Background:
- Understanding molecular state dynamics is crucial for various applications.
- Electron-impact excitation is a key process in molecular physics.
- Polarization measurements provide insights into molecular symmetries and coupling schemes.
Purpose of the Study:
- To measure the polarization of Fulcher-band fluorescence from electron-impact excitation of H2 and D2.
- To investigate the production of specific molecular magnetic substates (M(N)=0).
- To probe the orientation of rotationally resolved molecular states and test theoretical models.
Main Methods:
- Spin-polarized electron-impact excitation of H2 and D2 targets.
- Measurement of linear (P1) and circular (P3) polarization of Fulcher-band fluorescence.
- Analysis of d 3Π(u) → a 3Σ(g)+ transitions for electron energies from 14.3 to 28.5 eV.
Main Results:
- Linear polarization (P1) shows a transition from positive to negative values near threshold, indicating M(N)=0 state production.
- Nonzero circular polarization (P3) was measured, signifying molecular state orientation.
- P3 for Q-branch transitions aligns with Hund's case (b) theory, while R-branch deviations suggest Σ-symmetry perturbations.
Conclusions:
- Electron-impact excitation dynamics lead to specific molecular state populations.
- Molecular state orientation is experimentally confirmed and can be theoretically modeled.
- Deviations in R-branch polarization highlight the influence of state perturbations on molecular dynamics.
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