Long-range interactions from the self-broadened profile of Zn (4¹P₁–4¹S₀) and Cd (5¹P₁–5¹S₀) lines: correction of the interaction potential parameters

Abstract

The self-broadened absorption profile of Zn (213.8 nm) and Cd (228.8 nm) lines are measured and carefully analysed. The interaction potentials for the electronic states 0 + u and 1 u dissociating into (4 1 P 1 + 4 1 S 0 ) and (5 1 P 1 + 5 1 S 0 ) for Zn 2 and Cd 2 , respectively, are derived in the long-range region of (11-25) Å. It is found that although the resonance dipole-dipole interactions, C m 3 /R 3 , dominate in this region, the higher order van der Waals terms, C m 6 /R 6 are also not negligible. The coefficients C m 3 and the differences C m 6 between C m 6 for each of the 0 + u and 1 u excited states and C g 6 for the ground state of both molecules are determined. For the energy in eV and R in Å it is found that C 0 3 = −23.74 ± 0.40, C 0 6 = −483 ± 30 and C 1 3 = 11.87 ± 0.20, C 1 6 = −227 ± 20 for Zn 2 , as well as C 0 3 = −24.54 ± 0.10, C 0 6 = −280 ± 15 and C 1 3 = 12.27 ± 0.05, C 1 6 = −215 ± 10 for Cd 2 . A problem of the C g 6 coefficient for the considered systems is discussed accepting finally the following values: −178 ± 10 and −291 ± 15 eV Å6 for Zn 2 and Cd 2 , respectively. Thus, for the excited states involved, one obtains C 0 6 = −661 ± 40 and C 1 6 = −405 ± 30 for Zn 2 as well as C 0 6 = −571 ± 30 and C 1 6 = −506 ± 25 for Cd 2 . The C 6 m coefficients have never been determined experimentally in any of these cases and only for Zn 2 were they calculated by Ellingsen et al (2001 J. Phys. B: At. Mol. Opt. Phys. 34 2313) by means of a time-dependent gauge-invariant method-a variation-perturbation approach. Our experimental results for this case agree very well with theoretical predictions.

Two-dipole and three-dipole interaction coefficients of GROUP XII elements

“…We have already seen from Table III that their values for C 6 were large as compare to our and the experimental results [57,58]. Consequently, on the basis of good agreement between the present and previously reported other theoretical and experimental values [56][57][58] (Table III) for the C 6 of homonuclear and heteronuclear dimers, gives us the confidence that the predicted threedipole coefficients for various interactions are quite reliable. Here, for the C 9 coefficients, we also observed the same trend as we have seen in the C 6 that the combinations which involve Cd atom in Tables V and VI, have higher value of C 9 dispersion coefficients with respect to the other combinations.…”

“…Further, we observe that our obtained coefficients for homonuclear combinations exhibit excellent agreement with the reported experiment results [57,58] for Cd-Cd and Hg-Hg dimers, where in the case of Zn-Zn, our result deviates from the measurement by ∼ 10%. The overall good agreement of our results with the previously published works [38,[56][57][58] gives us confidence that the dispersion coefficients (C 6 ) obtained by us for different combinations between group XII atoms and their ions which are summarised in Table IV are quite reliable.…”

“…On comparison, we find that the values calculated by Qiao et al [38] for all combinations are over-estimated by their method as compare to our calculations. On the other hand, Grycuk et al [56] have computed the dispersion coefficients only for homonuclear dimers, and their results match considerably with the present calculated values. One can also see from the Table III that the values of Qiao et al [38] drastically differ from the results of Grycuk et al [56].…”

“…On the other hand, Grycuk et al [56] have computed the dispersion coefficients only for homonuclear dimers, and their results match considerably with the present calculated values. One can also see from the Table III that the values of Qiao et al [38] drastically differ from the results of Grycuk et al [56]. Further, we observe that our obtained coefficients for homonuclear combinations exhibit excellent agreement with the reported experiment results [57,58] for Cd-Cd and Hg-Hg dimers, where in the case of Zn-Zn, our result deviates from the measurement by ∼ 10%.…”

“…This will ascertain the accuracy of our present method used to evaluate the dispersion coefficients for other combinations. The values of C 6 for homonuclear and heteronuclear dimers are listed in Table III and compared with other theoretical [38,56] and experimental results [57,58]. On comparison, we find that the values calculated by Qiao et al [38] for all combinations are over-estimated by their method as compare to our calculations.…”