Harmonic progression

The non-zero numbers a, h, c, etc., form a harmonic progression if their reciprocals /a, /h, Jc, etc., form an arithmetic progression. 

The reciprocals of the terms of the arithmetic-progression series are called harmonic progression. No general summation formulas are available for this series. 

TABLE VI. OBSERVED VAN DER WAALS MODE FREQUENCIES AND HARMONIC PROGRESSIONS IN THE SPECTRA OF THE CLUSTERS. 

Weber et al have investigated van der Waals vibrational transitions in T Ar and other tetrazine-rare gas complexes. They observed that (i) the frequencies of these transitions in the cluster T X (X = Ar, Kr, Xe) fit fairly well in with harmonic or near harmonic progressions and (ii) the relative intensities of corresponding transitions of stretch vibrational modes are sensibly uncoupled, unless the vibrational mixing in the three different clusters would be very similar. 

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