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Register a new userEnergy and radiative properties of the (3)1{Pi} and (5)1{Sigma}+ states of RbCs: Experiment and theory
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We combined high-resolution Fourier-transform spectroscopy and large-scale electronic structure calculation to study energy and radiative properties of the high-lying (3)1{Pi} and (5)1{Sigma}+ states of the RbCs molecule. The laser-induced (5)1{Sigma}+(4)1{Sigma}+(3)1{Pi}-A(2)1{Sigma}+ b(1)3{Pi} fluorescence (LIF) spectra were recorded by the Bruker IFS-125(HR) spectrometer in the frequency range { u} 5500 to 10000cm-1 with the instrumental resolution of 0.03 cm-1. The rotational assignment of the observed LIF progressions, which exhibit irregular vibrational-rotational spacing due to strong spin-orbit interaction between A1{Sigma}+ and b3(Pi) states was based on the coincidences between observed and calculated energy differences. The required rovibronic term values of the strongly perturbed A-b complex have been calculated by a coupled-channels approach for both 85Rb133Cs and 87Rb133Cs isotopologs with accuracy of about 0.01 cm-1, as demonstrated in A. Kruzins et al. [J. Chem. Phys. 141, 184309 (2014)]. The experimental energies of the upper (3)1(Pi) and (5)1{Sigma}+ states were involved in a direct-potential-fit analysis performed in the framework of inverted perturbation approach. Quasirelativistic ab initio calculations of the spin-allowed (3)1{Pi},(5)1{Sigma}+- (1-4)1{Sigma}+(1-3)1{Pi} transition dipole moments were performed. Radiative lifetimes and vibronic branching ratios of radiative transitions from the (3)1{Pi} and (5)1{Sigma}+ states were evaluated. To elucidate the origin of the {Lambda}-doubling effect in the (3)1{Pi} state, the angular coupling (3)1{Pi}-(1-5)1{Sigma}+ electronic matrix elements were calculated and applied for the relevant q-factors estimate. The intensity distributions simulated for the particular (5)1{Sigma}+(3)1{Pi}-A-b LIF progressions have been found to be remarkably close to their experimental counterparts.
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We present the first spectroscopic studies of the $C ^1Sigma^+$ electronic state and the $A ^1Sigma^+$ - $b ^3Pi_{0^+}$ complex in $^7$Li - $^{85}$Rb. Using resonantly-enhanced, two-photon ionization, we observed $v = 7$, 9, 12, 13 and $26-44$ of the $C ^1Sigma^+$ state. We augment the REMPI data with a form of depletion spectra in regions of dense spectral lines. The $A ^1Sigma^+$ - $b ^3Pi_{0^+}$ complex was observed with depletion spectroscopy, depleting to vibrational levels $v=0 rightarrow 29$ of the $A ^1Sigma^+$ state and $v=8 rightarrow 18$ of the $b ^3Pi_{0^+}$ state. For all three series, we determine the term energy and vibrational constants. Finally, we outline several possible future projects based on the data presented here.
A comprehensive study of the electronic states at the 4s+5s asymptote in KRb is presented. Abundant spectroscopic data on the astate state were collected by Fourier-transform spectroscopy which allow to determine an accurate experimental potential energy curve up to 14.8 AA . The existing data set (C. Amiot et al. J. Chem. Phys. 112, 7068 (2000)) on the ground state Xstate was extended by several additional levels lying close to the atomic asymptote. In a coupled channels fitting routine complete molecular potentials for both electronic states were fitted. Along with the line frequencies of the molecular transitions, recently published positions of Feshbach resonances in $^{40}$K and $^{87}$Rb mixtures (F. Ferlaino et al. Phys. Rev. A 74, 039903 (2006)) were included in the fit. This makes the derived potential curves capable for an accurate description of observed cold collision features so far. Predictions of scattering lengths and Feshbach resonances in other isotopic combinations are reported.
We present experimentally derived potential curves and spin-orbit interaction functions for the strongly perturbed $A^{1}Sigma_{u}^{+}$ and $b^{3}Pi_{u}$ states of the cesium dimer. The results are based on data from several sources. Laser-induced fluorescence Fourier transform spectroscopy (LIF FTS) was used some time ago in the Laboratoire Aim{e} Cotton primarily to study the $X ^{1}Sigma_{g}^{+}$ state. More recent work at Tsinghua University provides information from moderate resolution spectroscopy on the lowest levels of the $b^{3}Pi_{0u}^{pm}$ states as well as additional high resolution data. From Innsbruck University, we have precision data obtained with cold Cs$_{2}$ molecules. Recent data from Temple University was obtained using the optical-optical double resonance polarization spectroscopy technique, and finally, a group at the University of Latvia has added additional LIF FTS data. In the Hamiltonian matrix, we have used analytic potentials (the Expanded Morse Oscillator form) with both finite-difference (FD) coupled-channels and discrete variable representation (DVR) calculations of the term values. Fitted diagonal and off-diagonal spin-orbit functions are obtained and compared with {it ab initio} results from Temple and Moscow State universities.
In this work we report the opening of an energy gap at the filling factor $ u=3+1/3$, firmly establishing the ground state as a fractional quantum Hall state. This and other odd-denominator states unexpectedly break particle-hole symmetry. Specifically, we find that the relative magnitudes of the energy gaps of the $ u=3+1/3$ and $3+1/5$ states from the upper spin branch are reversed when compared to the $ u=2+1/3$ and $2+1/5$ counterpart states in the lower spin branch. Our findings raise the possibility that the former states have a non-conventional origin.
We investigate the dynamics of molecular photoexcitation by unchirped femtosecond laser pulses using RbCs as a model system. This study is motivated by a goal of optimizing a two-color scheme of transferring vibrationally-excited ultracold molecules to their absolute ground state. In this scheme the molecules are initially produced by photoassociation or magnetoassociation in bound vibrational levels close to the first dissociation threshold. We analyze here the first step of the two-color path as a function of pulse intensity from the low-field to the high-field regime. We use two different approaches, a global one, the Wavepacket method, and a restricted one, the Level by Level method where the number of vibrational levels is limited to a small subset. The comparison between the results of the two approaches allows one to gain qualitative insights into the complex dynamics of the high-field regime. In particular, we emphasize the non-trivial and important role of far-from-resonance levels which are adiabatically excited through vertical transitions with a large Franck-Condon factor. We also point out spectacular excitation blockade due to the presence of a quasi-degenerate level in the lower electronic state. We conclude that selective transfer with femtosecond pulses is possible in the low-field regime only. Finally, we extend our single-pulse analysis and examine population transfer induced by coherent trains of low-intensity femtosecond pulses.
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