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H$_2^+$ spectroscopy

H$_2^+$ spectroscopy is performed using REMPD (resonance enhanced multiphoton dissociation). The experimental setup includes a linear ion trap, a Be$^+$ ion cooling plateform, a state selected H$_2^+$ source using 3+1 REMPI (resonance enhanced multiphoton dissociation) at 303 nm, a high finesse Fabry-Perot cavity for Doppler free two-photon spectroscopy using a SI-referenced 9.17 $\mu$m laser, a 213 nm dissociation laser. State selected ion production in the $v=0$ vibrational level has been evidenced (see the figure and [J. Schmidt & al, Phys. Rev. Appl. 14, 024053 (2020)]. The spectroscopy resolution is expected to be a few ten Hz. A 1.62 $\mu$m spectroscopy laser is in preparation.

Blue: Be$^+$ laser cooled ions.  Dark line : sympathetically cooled state selected H$_2^+$ ions.

SI-referenced lasers

A fceo-free frequency comb at 1.55 $\mu$m with extensions to 1.9 $\mu$m and 1.1 $\mu$m is optically locked to the REFIMEVE ultrastable signal. It is used to phase-lock all the laser involved in the experiments, and get SI-referenced laser frequencies. All the locks use the same Phase/Frequency comparator and proportional-integral (PI) developped by the LKB electronic work-shop.

Collaborations

Laboratoire de physique des lasers

Funding

ANR, Comb’IDF, First-TF, REFIMEVE

Left: Phase frequency comparator with 2, 4, 8 dividor. Right: Proportional-Integral corrector.
Exhaustive experimental sketch of the optical and electronic bench used to stabilize a CO$_2$ laser at 9.17 $\mu$m, the 1549 nm and 1051 nm lasers used for the Be$^+$ cooling tunable laser source. A continuous tuning range of 400 MHz at 1549 nm is obtained resulting in a tuning range of 800 MHz at 313 nm after sum frequency mixing and second harmonic generation. Not shown : optical bench for the phase-lock of a 1621 nm laser. High resolution image.

Molecular spectroscopy

Details in molecular rovibrational spectra can be particularly sensitive to the proton to electron mass ratio $\mu$. Combining ultrahigh resolution laboratory measurements to early universe radiotelescope spectra, one can probe spatial or time dependance of $\mu$ with improved accuracy.

This is the aim of the ANR Ulti$\mu$os project.

Collaborations & funding:

ANR Ulti$\mu$os project : Laboratoire de physique des lasers LPL, MONARIS

GBARproxy experiment

Text coming soon

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