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Register a new userPhotoassociative Spectroscopy of a Halo Molecule in $^{86}$Sr
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We present two-photon photoassociation to the least-bound vibrational level of the X$^1Sigma_g^+$ electronic ground state of the $^{86}$Sr$_2$ dimer and measure a binding energy of $E_b=-83.00(7)(20)$,kHz. Because of the very small binding energy, this is a halo state corresponding to the scattering resonance for two $^{86}$Sr atoms at low temperature. The measured binding energy, combined with universal theory for a very weakly bound state on a potential that asymptotes to a van der Waals form, is used to determine an $s$-wave scattering length $a=810.6(12)$,$a_0$, which is consistent with, but substantially more accurate than the previously determined $a=798(12),a_0$ found from mass-scaling and precision spectroscopy of other Sr isotopes. For the intermediate state, we use a bound level on the metastable $^1S_0-{^3P_1}$ potential. Large sensitivity of the dimer binding energy to light near-resonant with the bound-bound transition to the intermediate state suggests that $^{86}$Sr has great promise for manipulating atom interactions optically and probing naturally occurring Efimov states.
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We demonstrate photoassociation (PA) of ultracold fermionic $^{87}$Sr atoms. The binding energies of a series of molecular states on the $^1Sigma^+_u$ $5s^2,^1$S$_0+5s5p,^1$P$_1$ molecular potential are fit with the semiclassical LeRoy-Bernstein model, and PA resonance strengths are compared to predictions based on the known $^1$S$_0+^1$S$_0$ ground state potential. Similar measurements and analysis were performed for the bosonic isotopes $^{84}$Sr and $^{86}$Sr, allowing a combined analysis of the long-range portion of the excited-state potential and determination of the $5s5p,^1$P$_1$ atomic state lifetime of $5.20 pm 0.02$ ns. The results enable prediction of PA rates across a wide range of experimental conditions.
We present results from two-photon photoassociative spectroscopy of the least-bound vibrational level of the X$^1Sigma_g^+$ state of the $^{88}$Sr$_2$ dimer. Measurement of the binding energy allows us to determine the s-wave scattering length, $a_{88}=-1.4(6) a_0$. For the intermediate state, we use a bound level on the metastable $^1S_0$-$^3P_1$ potential, which provides large Franck-Condon transition factors and narrow one-photon photoassociative lines that are advantageous for observing quantum-optical effects such as Autler-Townes resonance splittings.
Motivated by recent interest in low dimensional arrays of atoms, we experimentally investigated the way cold collisional processes are affected by the geometry of the considered atomic sample. More specifically, we studied the case of photoassociative ionization (PAI) both in a storage ring where collision is more unidirectional in character and in a trap with clear undefinition of collision axis. First, creating a ring shaped trap (atomotron) we investigated two-color PAI dependence with intensity and polarization of a probing laser. The intensity dependence of the PAI rate was also measured in a magneto-optical trap presenting equivalent temperature and density conditions. Indeed, the results show that in the ring trap, the value of the PAI rate constant is much lower and does not show evidences of saturation, unlike in the case of the 3D-MOT. Cold atomic collisions in storage ring may represent new possibilities for study.
We propose and experimentally investigate a scheme for observing Feshbach resonances in atomic quantum gases in situ and with a high temporal resolution of several ten nanoseconds. The method is based on the detection of molecular ions, which are optically generated from atom pairs at small interatomic distances. As test system we use a standard rubidium gas (87Rb) with well known magnetically tunable Feshbach resonances. The fast speed and the high sensitivity of our detection scheme allows to observe a complete Feshbach resonance within one millisecond and without destroying the gas.
A combined experimental and theoretical spectroscopic study of high-$n$, ${30 lesssim n lesssim 100}$, triplet $text{S}$ and $text{D}$ Rydberg states in $^{87}text{Sr}$ is presented. $^{87}text{Sr}$ has a large nuclear spin, ${I=9/2}$, and at high-$n$ the hyperfine interaction becomes comparable to, or even larger than, the fine structure and singlet-triplet splittings which poses a considerable challenge both for precision spectroscopy and for theory. For high-$n$ $text{S}$ states, the hyperfine shifts are evaluated non-perturbatively taking advantage of earlier spectroscopic data for the ${I=0}$ isotope $^{88}text{Sr}$, which results in good agreement with the present measurements. For the $text{D}$ states, this procedure is reversed by first extracting from the present $^{87}text{Sr}$ measurements the energies of the $^{3}text{D}_{1,2,3}$ states to be expected for isotopes without hyperfine structure ($^{88}text{Sr}$) which allows the determination of corrected quantum defects in the high-$n$ limit.
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