The lowest electronic states of Mg2 according to ab initio calculations by Czuchaj et al. 17 Thick lines indicate potentials, which are important for the present work.
Part of the recorded absorption spectrum (black, full line) together with the simulated spectrum (red, dotted) assuming constant electronic transition dipole moment and proper isotopic ratios of 24Mg2 (62%), 24Mg25Mg (7.9%), and 24Mg26 (8.7%), respectively. The upper (blue) trace shows the difference between measured and simulated spectra on the same signal scale.
Example of a fluorescence progression with P(12)/R(10) doublets, where R(10) (3−5) of 24Mg2 was excited at 26 499.328 cm−1 derived by a frequency doubled TiSa laser.
Range of vibrational quantum numbers v” and rotational quantum numbers J” of the energy levels used for the characterization of the ground state of Mg2 in the present study. The data on 26Mg2 were taken from Ref. 12 .
Comparison of potential energy curves. Black, solid: U X - U MLR , red, dashed: U X - U TT , blue, dotted: U X - U Cheb . The range of internuclear distances covered by the data is indicated by the vertical dashed lines.
Comparison of level energy differences v”,J” = 0 with respect to the X-representation calculated from the various potential models (MLR: full squares, TT: full triangles, Chebychey: full circles), for details see text. The differences with term energies from Ref. 16 (open squares) are calculated with the Dunham parameters of their Table IV , and differences with level energies from Ref. 18 (open triangles) are calculated using the spline interpolated IPA potential of their Table II . Lines connecting the points are only drawn for guiding the eye.
Parameters for the potential curve of the ground state of Mg2 for the X-representation. See text for details of the short-range representation.
Parameters for the potential curve of the ground state of Mg2 for the MLR representation.
Parameters for the potential curve of the ground state of Mg2 for the modified Tang-Toennies representation.
Parameters for the potential curve of the ground state of Mg2 for the Chebychev expansion model.
Dissociation energies derived by the different models for 24Mg2. The averages are calculated only from the models X, MLR, and TT, which employ the same long-range parameters C n . The uncertainties given for the averages of D e and D0 include the standard deviation and the influence of the uncertainties of the long-range parameters given in Ref. 20 for C6 and C8, assuming 10% uncertainty of C10. For E(v” = 0, J” = 0), we give the standard deviation.
Scattering lengths derived from the different potential approaches. The results for the Chebychev model are not included in the average because its long-range behavior is different due the missing C10 contribution.
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