Efimov Resonance and Three-Body Parameter in a Lithium-Rubidium Mixture

We study collisional heating in a cold ^{7}Li-^{87}Rb mixture near a broad Feshbach resonance at 661 G. At the high field slope of the resonance, we find an enhanced three-body recombination rate that we interpret as a heteronuclear Efimov resonance. With improved Feshbach spectroscopy of two further resonances, a model for the molecular potentials has been developed that now consistently explains all known Feshbach resonances of the various Li-Rb isotope mixtures. The model is used to determine the scattering length of the observed Efimov state. Its value of -1870a_{0} Bohr radii supports the currently discussed assumption of universality of the three-body parameter also in heteronuclear mixtures.

Rotationsspektrum von BaO / Rotational Spectrum of BaO

With the new saturation modulation the rotational spectrum of BaO was measured. The accuracy of the derived molecular constants is about an order of magnitude higher than in previous studies and some discrepancies are removed. It was demonstrated that measurements of the electric dipole moment are possible with microwave spectroscopy up to temperatures of 2000 K.

Adiabatische Korrektur der Born-Oppenheimer-Näherung beim PbS/Adiabatic Correction of the Born-Oppenheimer Approximation of PbS

The rotational microwave spectrum of PbS was measured in a frequency range from 65 to 105 GHz in order to determine the higher order isotopic effect of the rotational constant. From this we deduce (by calculating the nonadiabatic and the Dunham-correction) the adiabatic correction of the Born-Oppenheimer approximation, which depends linearly on the reciprocals of the masses of the two atoms in a diatomic molecule. Because of the small mass variation by isotopic substitution for the heavier molecules of the IV/VI-compounds the relative accuracy of the primary measurements must be of the order of 10-6 . The least square fit of 112 rotational transitions yields a relative error of 10-7 for the rotational constant Y01 . The adiabatic corrections from Pb and S differ by a factor of 50, which was unexpected.

Hyperfine Structure in the Rotational Spectrum of GaBr

The hyperfine structure of the rotational transition J = 2 ← 1 in the vicinity of 9.8 GHz was measured. The analysis yielded the following quadrupole coupling constants:

e qv Q (79Br) = 105.78(34) + 0.92 (38) (ν + 1/2) MHz,

e qv Q (81Br) = 88.55(35) + 0.60(32) (ν + 1/2) MHz,

e qv Q (69Ga) = -86 .6 8(30) + 0.36 (24) (ν + 1/2) MHz,

e q0 Q (71Ga) = - 54.58 (25) MHz.

These results are consistent with systematic trends in the group of (III a/VII a)-compounds and remove some discrepencies in the literature.

New spectroscopic data, spin-orbit functions, and global analysis of data on the AΣu+1 and bΠu3 states of Na2

The lowest electronically excited states of Na2 are of interest as intermediaries in the excitation of higher states and in the development of methods for producing cold molecules. We have compiled previously obtained spectroscopic data on the A 1Sigmau+ and b 3Piu states of Na2 from about 20 sources, both published and unpublished, together with new sub-Doppler linewidth measurements of about 15,000 A<--X transitions using polarization spectroscopy. We also present new ab initio results for the diagonal and off-diagonal spin-orbit functions. The discrete variable representation is used in conjunction with Hund's case a potentials plus spin-orbit effects to model data extending from v=0 to very close to the 3 2S+3 2P12 limit. Empirical estimates of the spin-orbit functions agree well with the ab initio functions for the accessible values of R. The potential function for the A state includes an exchange potential for S+P atoms, with a fitted coefficient somewhat larger than the predicted value. Observed and calculated term values are presented in an auxiliary (EPAPS) file as a database for future studies on Na2.

The AΣu+1 state of K2 up to the dissociation limit

We report an experimental study of the K(2) A (1)Sigma(u) (+) state. Long-range levels up to the dissociation limit were observed in a two laser spectroscopic experiment using a highly collimated molecular beam. We derive an analytical potential energy curve for the complete A state including long-range dispersion terms. From these, we obtain radiative atomic lifetimes of 26.74(3) ns for the 4p(1/2) state and 26.39(3) ns for the 4p(3/2) state of (39)K. The dissociation energy of the X (1)Sigma(g) (+) ground state with respect to v=0, J=0 is found to be D(0)=4404.808(4) cm(-1).

High resolution spectroscopy and potential determination of the (3)Π1 state of NaCs

The (3)(1)Pi state of the NaCs molecule was studied by high resolution Fourier-transform spectroscopy. The (3)(1)Pi-->X (1)Sigma(+) laser induced fluorescence was excited by an Ar(+) ion laser or by a single-mode frequency-doubled cw Nd:YAG laser. The presence of argon buffer gas yielded rich rotational relaxation spectra allowing to enlarge the data set for the (3)(1)Pi state term values, as well as to observe Lambda splittings in a wide range of vibrational (v(')) and rotational (J(')) quantum numbers. The data field includes about 820 energy levels of (3)(1)Pi NaCs in the range from v(')=0 to 37 and from J(')=3 to 190, which corresponds to ca. 95% of the potential well depth. Direct fit of the potential energy curve to the level energies is realized using the inverted perturbation approach method; a set of Dunham coefficients is also presented.

Creation of a dipolar superfluid in optical lattices

We show that, by loading a Bose-Einstein condensate of two different atomic species into an optical lattice, it is possible to achieve a Mott-insulator phase with exactly one atom of each species per lattice site. A subsequent photoassociation leads to the formation of one heteronuclear molecule with a large electric dipole moment, at each lattice site. The melting of such a dipolar Mott insulator creates a dipolar superfluid, and eventually a dipolar molecular condensate.

Level-splitting effects in resonant four-wave mixing

Resonant spectral structures of four-wave mixing (FWM) in molecular sodium are investigated. For a double- ? configuration with strong-weak-strong-weak fields, split components in FWM spectra induced by the strong pump fields are observed. It is shown that the split components merge into a single peak for a certain ratio of the strong field intensities. A correlation between the level-splitting effects and the saturation behavior of the FWM signal is experimentally demonstrated.

Photoassociation of cold Ca atoms

We present the first measurement of a photoassociative spectrum of an alkaline earth element near the dissociation limit. The observed spectrum of Ca2 formed from cold atoms shows the regular vibrational series with the characteristic spacing of the 1/R3 asymptotic potential. The interpretation is in principle simplified compared to previous measurements on alkali metals by the nondegenerate ground state and the missing hyperfine structure of 40Ca. As an example, we derive the natural decay rate of the excited atomic 4p 1P1 state from the positions of the observed vibrational and rotational resonances with reduced uncertainty compared to previous measurements.

First Observation of Hyperfine Structure in K(2)

The hyperfine structure of the (v'-v") = (27-0) band of the b(3)Pi(u0(+)) <-- X(1)Sigma(+)(g) transition has been observed by laser excitation spectroscopy in a highly collimated molecular beam. Hyperfine parameters for magnetic dipole and electric quadrupole interaction are derived from least-squares fitting of the hyperfine pattern and deperturbation between A(1)Sigma(+)(u) and b(3)Pi(u0(+)). Copyright 2000 Academic Press.

REMPI Spectroscopy of SO Singlet States

Three newly found vibrational levels at energies Te(v) = 45127.88(3), 51900.40(4), and 52604.95(3) cm-1 allow the first application of resonance-enhanced multiphoton ionization for detecting the SO radical in its low-energy singlet states, a1Delta and b1Sigma+. The analysis of the spectra is based on the observation of 10 rotationally resolved bands starting from a1Delta v = 0, 6 ellipsis 11 and b1Sigma+ v = 8, covering a typical range of J = 5 ellipsis 40 or 50. Population of these SO singlet states has been achieved by two-photon dissociation of SO2 in a molecular beam environment, applying wavelengths in the 248 to 291 nm range. This paper presents an analysis of the rotational, vibrational, and electronic properties of the new levels. Reviewing earlier works on the singlet states of SO, a revised term energy scheme is provided which connects the singlet and triplet systems of the molecule. Copyright 1998 Academic Press.

Continuous resonant four-wave mixing in double-Lambda level configurations of Na(2)

Efficient continuous resonant frequency mixing omega(4) = omega(1) - omega(2) + omega(3) in Na(2) has been realized. A bichromatic field (lambda(1) = 488 nm, lambda(2) = 525 nm), generated by an Ar(+)-laser-pumped Na(2) Raman laser, and radiation at lambda(3) = 655 nm from a dye laser interact resonantly with corresponding transitions X(1)Sigma(g)(+)(upsilon = 3, J = 43) ? B(1)Pi(u)(6, 43) ? X(1)Sigma(g)(+)(13, 43) ? A(1)Sigma(g)(+)(24, 44) in a test Na(2) heat pipe. For input powers of 200, 25, and 400 mW an output beam of as much as 0.2 mW at lambda(4) = 599 nm has been observed. Measured parameter dependences indicate an influence of interference effects. This is directly related to the discussion of lasing without inversion.