[en] We have performed high precision photoassociation spectroscopy of ultracold cesium gas. Using trap-loss fluorescence detection and controlling the background cesium pressure we were able to photoassociate atoms into excited states of ultracold molecules with large detunings up to 56 cm-1 below the Cs(6S_1/2)+Cs(6P_1/2) atomic asymptote. Vibrational progressions are assigned to 0_g^-, 0_u⁺, and 1_g long-range states. By fitting the spectral data to the LeRoy-Bernstein expression, the effective coefficients of the leading long-range interactions and the vibrational quantum number at dissociation are obtained. In addition we have observed spectral perturbations between states of the same symmetry belonging to different asymptotes (6P_1/2 and 6P_3/2). The perturbations are manifested through irregular vibrational level spacings and are especially pronounced in the 0_u⁺ symmetry. Many observed rotational levels indicate d- and higher partial wave contributions to the photoassociation cross section in the presence of trapping laser light, while spectral regions with only weak features suggest nodes in the lower state wave functions corresponding to the two ground state atoms asymptote

[en] The cooling and trapping of atoms and atomic ions is a rapidly advancing field of fundamental science (e.g., Bose-Einstein condensation). We are attempting to extend the field to neutral molecules as well. As a first step, we are studying single- and multicolor photoassociation of ultracold (∼300 μK) ³⁹K atoms confined in a magneto-optical trap. Photoassociation of ultracold atoms (as opposed to thermal atoms) includes sharp resonances with wavelength as long-range rovibrational levels (outer turning points of tens or hundreds of Bohr) are accessed from colliding atomic pairs with ∼10 MHz of relative kinetic energy and only a few partial waves (l=0,1,2). Potential energy curves derived from these spectra test electronic structure and long-range perturbation theory calculations of interatomic potentials. In particular, such studies yield the full set of potential energy curves needed for fully quantum calculations of atomic line broadening at any temperature

[en] High precision photoassociation spectroscopy is performed in ultracold cesium gas, with detunings as large as 51 cm-1 below the Cs(6S_1/2)+Cs(6P_3/2) asymptote. Trap-loss fluorescence detection is used for detecting the photoassociation to excited state ultracold molecules. Long vibrational progressions are assigned to electronic states of 0_g^-, 0_u⁺, and 1_g symmetry. The spectral data are fitted to a LeRoy-Bernstein equation, in order to obtain the effective coefficients of the leading long-range interaction term (C₃/R³) and the relative vibrational quantum numbers measured down from dissociation. Additionally we present evidence for perturbations between the 0_g^- state and the dark 2_u state

[en] We present a simple model of ultracold cesium dimer formation in which the photoassociation into rovibrational levels of the double-minimum Cs₂ 3 ¹Σ_u⁺ state above its internal barrier enables spontaneous or stimulated emission into the lowest rovibrational levels of the Cs₂ 1(X) ¹Σ_g⁺ ground electronic state. The transition dipole moment should be sufficiently large for observation of such spectral transitions. The use of the Cs₂ 3 ¹Σ_u⁺ double-minimum potential could be extended to molecular Bose-Einstein condensates in which an optical trap can be employed for trapping of both atomic and molecular species

[en] We report analyses and comparison of three high quality ab initio KRb a ³Σ⁺ state potentials [Rousseau et al., J. Mol. Spectrosc. 203, 235 (2000); Park et al., Chem. Phys. 257, 135 (2000); Kotochigova et al., Phys. Rev. A 68, 011501 (2003)]. Eigenvalues for all vibrational levels and precision binding energies for high-lying levels (and corresponding triplet scattering lengths) are presented. By adjusting the inner wall of a potential, we show that we can reproduce measured scattering lengths of two isotopomers and predict scattering lengths of all isotopomers

[en] We report new results on the spectroscopy of the 3 ³Σ⁺ electronic state of ³⁹K⁸⁵Rb. The observations are based on resonance-enhanced multiphoton ionization of ultracold KRb molecules starting in vibrational levels v′′ = 18–23 of the a ³Σ⁺ state and ionized via the intermediate 3 ³Σ⁺ state. The a-state ultracold molecules are formed by photoassociation of ultracold ³⁹K and ⁸⁵Rb atoms to the 3(0⁺) state of KRb followed by spontaneous emission. We discuss the potential applications of this state to future experiments, as a pathway for populating the lowest vibrational levels of the a state as well as the X state

[en] We present perturbations in photoassociation spectra of ultracold caesium. High-precision photoassociation spectra up to 54 cm^-1 below the Cs (6S_1/2)+Cs(6P_1/2) asymptote revealed perturbations related to resonant coupling between electronic states of the same symmetry but belonging to different asymptotes. The perturbations, which are manifested as irregularities in vibrational level spacings, are most pronounced for the 0_u⁺ state, but to some extent present in the 1_g and 0_g^- states, which are also affected by predissociation. We have performed theoretical calculations of perturbations for all three states and found qualitative agreement with the experimental results

[en] Atomic line self-broadening was observed in ultracold cesium. Using resonant ionization detection we were able to photoassociate atoms into excited states of ultracold molecules below the second excited PJ atomic asymptotes Cs(6S1/2) + Cs(7P1/2) and Cs(6S1/2) + Cs(7P3/2). We were able to observe blue detuned satellite band features at 560 MHz and 800 MHz above the 7P1/2 and 7P3/2 atomic limits, respectively, as well as sharp hyperfine split features on the blue and red side of the atomic resonances. Such spectral features can be qualitatively supported by the local maxima in the long range molecular structure beyond 50 A

[en] We have observed atomic line self-broadening of Cs near 7P_3/2 and 7P_1/2 atomic lines at ultracold temperatures using a magneto-optical trap and resonant ionization detection. We have observed blue satellite band features at detunings of 560 and 800 MHz, respectively, as well as sharp hyperfine-split photoassociative spectra on the red wings of each line and also on the blue wings. Possible explanations of these features are discussed

[en] We show that the multiplicative product of a molecular-beam excitation spectrum and an ultracold-molecule excitation spectrum, with a frequency offset appropriate to the initial ultracold-molecule level, provides the relative rate of stimulated Raman transfer (SRT) from a given high rovibrational level to the lowest rovibronic level, i.e., the v^''=0,J^''=0 level of the ground electronic state for photoassociated (and magnetoassociated) ultracold molecules. This product spectrum clearly indicates the optimal pathways for SRT, even when the two component spectra are completely unassigned. We illustrate this specifically for the case of KRb.