vibrational partition function based on low-resolution IR measurements by
J. L. Duncan et al., J. Mol. Spectrosc. 69 (1978) 123;
doi:10.1016/0022-2852(78)90033-4.

Estimated fundamentals up to 2200 cm-1:
nu6:  1446.95
nu3: ~1380
nu7:  1028.11
nu4:   899.10
nu8:   356.43

500: 3.0749
300: 1.5366
225: 1.2490
180: 1.1282
150: 1.0692
120: 1.0285
100: 1.0120
 75: 1.0021