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tional online material. 

For the convenience of the reader we also made fits us- ing the MLR potential description from [29], which might allow for defining the potential by a lower number of pa- rameters. It has the mathematical form 

<img src='content_image/379736.jpg'>

with the long-range function 

and the exponential function 

<img src='content_image/379738.jpg'>

where 

Three mapping functions y a b are defined as 

where the placeholder a can either be ’ e ’ for the equi- librium radius R$_{e}$ or ’ ref ’ for R$_{ref}$ and the exponent b can either be p or q . R$_{ref}$ is an expansion point at an internuclear distance larger than R$_{e}$ . The β$_{i}$ , C$_{i}$ , R$_{e}$ , and the dissociation energy D$_{e}$ are the fit parameters, while the parameter R$_{ref}$ and the exponents p and q are man- ually chosen to optimize the potential description with a minimum number of coefficients and to get the proper long range behavior. 

The potential coefficients for the MLR description are given in table III, the normalized standard deviation is σ = 0 . 80 as for the description given in table I. Thus there is no significant difference in the quality of the de- scription of the data set. The clear advantage of the 

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potential description from table III compared to the po- tential description from table I is the lower number of potential coefficients necessary (14 β$_{i}$ instead of 20 a$_{i}$ ) and the fact that it is indefinitely continuously differen- tiable at all points which is not the case for the poten- tial of table I at the points R$_{i}$ and R$_{a}$ . Disadvantages are the much more complex formula with three mapping functions instead of one and a much stronger correlation of the long range coefficients C$_{i}$ with the potential co- efficients β$_{i}$ (see eqn (5)). For the potential description from table I the correlation between the C$_{i}$ and the a$_{i}$ is only due to the integration of the wave functions over the full potential region. Thus we applied the recommended C$_{i}$ values from table II for the fit of the MLR potential. The dissociation energy obtained in the MLR approach 

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