As the spectroscopic quantities of interest, we choose the vibrational fundamental and the first five harmonics, i.e., the intervals 𝐸 with 1 𝑣 6. Experimental values have been reported by Douay et al. We restrict attention to the range of distances that correspond to the classical turning points on g2(R) for v = 8, which allows a margin for disagreement between g2(R) and our final high-level potential. Those turning points (R = 1.07637 and 1.52955 Å) are the two initial points computed at the CCSDT(Q) level. Using a linear function as fM(R), eq. ( ) yields continuous potential-energy functions E1(R) (from the CASSCF guiding potential) and E2(R) (from MRCI+Q). The spectroscopic quantities are computed using E1(R) and using E2(R); the root-mean-square difference (RMSD) of the results is evaluated as 150.96 cm -1 , which is very large, indicating that another point is needed. The difference E2(R) -E1(R) is computed over a grid of distances covering the range of attention. The difference of largest magnitude is at R = 1.31952 Å, which is then computed at the high level. With three high-level points in hand, a quadratic function is used as fM and the process repeated. The RMSD drops below 1 cm -1 with only seven points, terminating the algorithm. The numerical results are summarized in Table and the resulting potential-energy functions are shown in Figure . The location of points in Figure may not match intuitive expectations. For example, there is no point near Re and the points do not occur as pairs of turning points. Moreover, seven points is fewer than might be selected merely from intuition. For example, one might choose the two turning points for each vibrational level of interest. That would be 14 points for 0 𝑣 6. This suggests an improvement in computational efficiency from guided point-selection: fewer expensive calculations are needed.