Examples of RbCs B → X LIF spectra from v′ = 0, 1, and 2, which contain one strong LIF progression. Laser excitation frequency for the B-state (v′, J′)-level are: (a) 13 644.754 cm−1 for (0, 153); (b) 13 643.94 cm−1 for (1, 127); (c) 13 795.015 cm−1 for (2, 89). All three spectra contain also several much weaker progressions. No spin-forbidden transitions to the a 3Σ+ state are observed.
A zoomed in fragment of the spectrum shown in Fig. 2(a) demonstrating rotational relaxation. The directly excited LIF lines (shown by arrows) correspond to the B(0, 153) → X(4, 152; 154) transition. Q-, P-, and R-lines from the levels populated by collisions are marked by bars below the spectrum.
J ′-dependence of the experimental term values of 85Rb133Cs in the reduced energy scale E red = E − 0.0132J ′(J ′ + 1) (v′-numbering is shown on the right side). Green triangles mark the levels from which LIF to the a(1)3Σ+ state was observed. Stars above J ′ = 0 presents the data from Ref. 25 , which are identified as v′-levels of the B(1)1Π state (their v′ numbers are marked nearby). Lines are calculated from the present PEC. Dotted lines are extrapolation.
J ′-dependence of the rotational constant for v′ = 0. Inset demonstrates a relatively weak perturbation of e-component centered at J ′ = 130.
J ′-dependence of the differences between the measured 85Rb133Cs term values E obs and their counterparts E calc calculated using the data from Tables I and II . Horizontal lines indicate the experimental uncertainty ±0.01 cm−1.
Present empirical and ab initio PECs of the B 1Π state: red points – present empirical, black solid line – ab initio calculations 14 in Hund's “c” coupling case, solid blue line – ab initio calculations 13 in Hund's “a” coupling case. Dotted lines represent the respective difference-based PECs: black – for Hund's “c” coupling case, 14 blue – for Hund's “a” coupling case. 13 Inset shows PECs close to their minima.
J ′-dependence of present experimental term values of 87Rb133Cs in the reduced energy scale E red = E − 0.0132J ′(J ′ + 1). Lines are calculated from the present empirical PEC. Red lines mark vibrational levels v′ = 0, 10, 20, 30, 40. The symbols are the same as in Fig. 4 .
The J ′(J ′ + 1)-dependence of local perturbation centers at of e-component only for v B ∈ [0, 3] (triangles). Solid lines correspond to the calculations based on Ref. 20 for . Dashed lines are calculated from the present B(1)1Π state PEC. Inset shows the difference between measured E obs and calculated E calc term values.
List of the grid points U(R) of the IPA potential for the 85Rb133Cs B(1)1Π state. Energies are given with respect to the minimum of the ground state.
The q 0 and q 1 values (in cm−1) fitted for the v′ ∈ [0, 2] levels of the B(1)1Π state of 85Rb133Cs.
Molecular constants for low-lying v′-levels of the B(1)1Π state of 85Rb133Cs. The J ′-range, the number of term energies (N) and the standard deviation (sd) are also presented. All constants are given in cm−1.
Comparison of molecular constants of the B(1)1Π state of 85Rb133Cs obtained in the present work with their counterparts obtained from perturbation analysis 25 and by ab initio calculations. 12–15,17 T e and ω e in cm−1, R e in Å. a — the ω e value is roughly estimated by a fit of vibrational differences, though its meaning is ambiguous because of negative anharmonicity.
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