ProductionandDetectionofUltracoldGroundState85Rb133CsMoleculesintheLowestVibrationalLevelbyShort-RangePhotoassociation

We investigate the production of ultracold ground state X1E+（v = 0） RbCs molecules in the lowest vibrational level via short-range photoassociation followed by spontaneous emission.The starting point is the laser cooled 85Rb and 133)Cs atoms in a dual species,forced dark magneto-optical trap.The special intermediate level（5）0+（v = 10） correlated to the（2）3Ⅱ electric state is achieved by the photoassociation process.The formed ground state X1E+（v = 0） molecule is resonantly excited to the 2～1Ⅱ intermediate state by a 651 nm pulse laser and is ionized by a 532 nm pulse laser and then detected by the time-of-flight mass spectrum.Saturation of the photoionization spectroscopy at large ionization laser energy is observed and the ionization efficiency is obtained from the fitting.The production of ultracold ground state 85Rb133Cs molecules is facilitative for the further research about the manipulation of ultracold molecules in the rovibrational ground state.