研究目的
To perform a precision measurement of the spin-rotation fine structure of metastable a 3Σ+u He2 molecules using Zeeman-decelerated samples to achieve high spectral resolution.
研究成果
The Zeeman deceleration method enabled precision measurements of spin-rotation intervals in metastable He2 with up to 300 Hz accuracy, improving previous results by an order of magnitude. The long interaction times from slow beams were key to high resolution. The technique is applicable to other open-shell molecules, advancing molecular spectroscopy.
研究不足
The method is limited to open-shell paramagnetic molecules. For higher rotational levels, the unresolved Zeeman substructure reduces measurement precision. Stray magnetic fields (~11 mG) cause sidebands and require shielding. The low molecular density and sensitivity to inhomogeneous fields may hinder further improvements like Ramsey-type experiments.
1：Experimental Design and Method Selection:
A multistage Zeeman decelerator is used to slow down and state-select molecules. Radio-frequency (rf) radiation is applied to induce transitions between spin-rotational components, and UV-laser ionization is used for detection. The method leverages the long interaction times due to low beam velocities for high precision.
2：Sample Selection and Data Sources:
A supersonic beam of metastable He2 molecules is produced from an electric discharge through a helium expansion, cooled to 10 K, with mean velocity around 500 m/s before deceleration.
3：List of Experimental Equipment and Materials:
Zeeman decelerator (55-stage), rf stripline, pulse-amplified cw ring dye laser, mumetal shield, microchannel-plate (MCP) detector, liquid helium for cooling.
4：Experimental Procedures and Operational Workflow:
Molecules are decelerated to velocities as low as 100 m/s. The rf pulse is applied to repopulate specific spin-rotational levels, followed by UV-laser excitation and ionization. Timing and pulse durations are optimized for maximum interaction time and minimal stray field effects.
5：Data Analysis Methods:
Transition frequencies are measured with precision up to 300 Hz. Zeeman shifts are calculated using angular momentum algebra, and spectra are fitted with Gaussian profiles. Centrifugal-distortion corrections are included in the Hamiltonian analysis.
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