EGAS41 - Swansea University

41 st EGAS CP 130 Gdańsk 2009
Fourier-transform spectroscopy studies
of the (4) 1 Σ + state of KCs
L. Busevica ∗ , I. Klincare, O. Nikolayeva, M. Tamanis, R. Ferber
Laser Centre, University of Latvia, 19 Rainis Boulevard, LV-1586 Riga, Latvia
∗ Corresponding author: Laureta.Busevica@lu.lv
The KCs molecule is expected to be a promising candidate to produce the ultracold
gas of polar molecules; in particular, due to the proximity of K(4p) and Rb(5p) atomic
asymptotes, the energy structure of KCs is the closest to the RbCs molecule which was
successfully produced in (v = 0)X 1 Σ + state at temperature 10 −4 K [1]. The empirical
potential energy curves of KCs ground X 1 Σ + and a 3 Σ + states have been recently obtained
[2]. As was revealed in [2], the excited (4) 1 Σ + state of KCs is connected to both X 1 Σ + and
a 3 Σ + states by optical transitions. Thus, the information on the (4) 1 Σ + state properties
could facilitate the selection of optical paths for efficient transformation of the respective
ultracold atoms into the absolute rovibrational ground state (v = 0, J = 0)X 1 Σ + of KCs;
till now the B(1) 1 Π state and the A(2) 1 Σ + − b(1) 3 Π system were considered for such
purpose.
This contribution presents first study of the (4) 1 Σ + state of KCs which has been
performed by Fourier-transform spectroscopy of laser induced fluorescence (LIF) using
a Bruker IFS125HR spectrometer with 0.03 cm −1 resolution. The KCs molecules were
produced at 280 o C either in a sealed cylindrical glass cell or in a heat-pipe containing
K (natural isotope mixture) and Cs metals. A single mode ring dye laser Coherent
699-21 with Rhodamine 6G dye was used as a light source; excitation frequencies varied
between 16800 cm −1 and 17300 cm −1 . Term values of the (4) 1 Σ + state have been obtained
by adding transition frequencies to the respective ground state (v X , J X )X 1 Σ + energies
calculated from [2]. The dependencies of the (4) 1 Σ + state term values on the factor
J(J+1) have been plotted spanning energy range from ca. 17000 cm −1 to 18000 cm −1 and
J range from 10 to 170. The experimental dependencies have been compared with their
theoretical counterparts based on calculations [3]; a preliminary vibrational identification
for the obtained (4) 1 Σ + state term values was suggested. Since both (4) 1 Σ + → X 1 Σ + and
(4) 1 Σ + → a 3 Σ + transitions have been observed in LIF spectra, the perturbation of the
(4) 1 Σ + state by a triplet state is expected. According to theoretical term schematics [3],
the (3) 3 Σ + and (2) 3 Π could be the perturbing states. The work on vibrational assignment
and potential energy curve construction of the (4) 1 Σ + state of KCs is currently in progress.
Acknowledgment
Support by Latvian Science Council grant No. 09.1036 is gratefully acknowledged.
References
[1] J.M. Sage, S. Sainis, T. Bergeman, D. DeMille, Phys. Rev. Lett. 94, 203001 (2005)
[2] R. Ferber, I. Klincare, O. Nikolayeva, M. Tamanis, A. Pashov, H. Knöckel, E. Tiemann,
J. Chem. Phys. 128, 244316 (2008)
[3] M. Korek et al., Can. J. Phys. 78, 977 (2000); M. Korek et al., J. Chem. Phys. 124,
094309 (2006); M. Aymar, O. Dulieu, private communications; J.T. Kim, Y. Lee, A.V.
Stolyarov, J. Mol. Spectr. (2009) doi:10.1016/j.jms.2009.02.011
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