Hyperfine structure in photoassociative spectra ofLi26and

Abstract

We present spectra of hyperfine resolved vibrational levels of the A 1 ⌺ u ϩ and 1 3 ⌺ g ϩ states of 6 Li 2 and 7 Li 2 obtained via photoassociation of colliding ultracold atoms in a magneto-optical trap. A simple first-order perturbation theory analysis accurately accounts for the frequency splittings and relative transition strengths of all observed hyperfine features. Assignment of the hyperfine structure allows accurate determination of a vibrational level center of gravity, which significantly decreases the experimental uncertainty of vibrational energies. Differences in the spectra of 6 Li 2 and 7 Li 2 are attributed to quantum statistics. The 1 3 ⌺ g ϩ series obeys Hund's case b ␤S coupling and the hyperfine constant is extracted for both isotopes.PACS number͑s͒: 33.15. Pw, 32.80.Pj, 33.20.Kf, 31.30.Gs Photoassociative spectroscopy of ultracold atoms is a powerful technique for probing long-range, high-lying vibrational levels of diatomic molecules with high precision ͓1͔. In this technique, a photoassociation laser is tuned to resonance between the unbound state of two colliding groundstate atoms and a bound excited-state vibrational level. For temperatures below 1 mK, which are easily attainable in laser-cooled optical traps, Doppler broadening is negligible and the spread in kinetic energies of the colliding atoms contributes an amount to the spectral width that is comparable to the natural linewidth of the transition. The high resolution inherent to this technique has enabled observations of molecular hyperfine structure in the singly excited electronic states of Li 2 ͓2,3͔, Na 2 ͓4-6͔, and Rb 2 ͓7,8͔. Numerically calculated adiabatic potentials incorporating hyperfine interactions have aided the assignment of electronic states ͓9͔ and the modeling of line shapes ͓10͔ in the photoassociation spectrum of Na 2 . In this paper, we identify the relevant hyperfine quantum numbers for photoassociative spectra of 6 Li 2 and 7 Li 2 reported previously ͓2͔ and show that the relative splittings and transition strengths of every hyperfine feature can be understood by simple analysis.The initial state consists of two colliding atoms, each in the 2s atomic state. Let i ជ 1 represent the nuclear spin of atom 1 and s ជ 1 be its electronic spin, so that f ជ 1 ϭ i ជ 1 ϩs ជ 1 is the total angular momentum of atom 1. Similarly, f ជ 2 is the total angular momentum of atom 2. The total molecular spin angular momentum isThe electronic orbital angular momentum L ជ and the nuclear orbital angular momentum l ជ combine to form the total molecular orbital angular momentum N ជ . The set of relevant quantum numbers iswhere ⌳ is the projection of L ជ on the internuclear axis and M N and M G are the projections of N ជ and G ជ on a laboratory fixed axis. The initial states are superpositions of eigenstates of the total electronic spin S ជ ϭs ជ 1 ϩs ជ 2 , so the colliding atoms interact via both the X 1 ⌺ g ϩ and the a 3 ⌺ u ϩ ground-state molecular potentials. In these states, ⌳ is zero. At zero magnetic field, the M N and M G st...

Anomalous Behavior of Dark States in Quantum Gases ofLi6

“…The results are summarized in Table I. We note that the molecular hyperfine splittings inferred from Table I differ from theory [31,32] by more than can be explained by the uncertainties of our measurements.…”

High-resolution photoassociation spectroscopy of the6Li2A(11Gunton1, Semczuk2, Dattani3 et al. 2013Phys. Rev. A181280View full textAdd to dashboardCite

“…Here, G = I + S and I = i 1 + i 2 is the total nuclear spin of the molecule, which can take on three possible values (I = 0,1,2) since the nuclear spin of each atom is i = 1. In the A(1 1 + u ) state, odd (even) N levels are (anti)symmetric upon atom exchange [21]. Thus, similar to the symmetry of G, odd values of N correspond to states with I = 0,2, and even values of N correspond to states with I = 1.…”

Hyperfine-Structure-Induced Purely Long-Range Molecules

“…Comprehensive discussions about the molecular symmetry in the asymptotic region are seen in Refs. [13][14][15]23], and the hyperfine structure has been analyzed in the region where the binding energies are much larger than the hyperfine splitting and is approximately a good quantum number [12,14,15]. As shown in Fig.…”