Hyperfine structure of weakly bound levels in the lowest 1g state of molecular 87Rb2
Chin-Chun Tsai, T Bergeman, Eite Tiesinga, Paul S. Julienne, D J. Heinzen
Photoassociation resonances in the 87Rb2 1g state dissociating to 52S+52P1/2 were produced by the excitation of colliding 87Rb atoms in a far-off resonance (FORT) trap. Levels down to 31 cm−1 below the dissociation limit were measured with resonance linewidths of 15 to 20 MHz, and have been located to a one-sigma combined systematic and statistical uncertainty of 100 MHz relative to the 52S + 52P1/2 limit. Electron and nuclear spins were fixed to a space-fixed axis by linearly polarized trapping light, so that only states with total nuclear spin I=3 were excited, thereby greatly simplifying the spectrum. The analysis of the data yielded hyperfine coupling parameters and vibrational, G(v), and rotational, B(v), parameters. The G(v) parameters could be fit to an rms accuracy of about 0.01 cm−1 to a potential constructed from current C3 and C6 long-range dispersion parameters plus an ab initio potential adjusted in depth and with a quadratic term (in the internuclear distance) added to the inner wall.