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:  1448.03
nu3: ~1390
nu7:  1036.37
nu4:   915.72
nu8:   356.88

500: 3.0490
300: 1.5340
225: 1.2475
180: 1.1276
150: 1.0706
120: 1.0283
100: 1.0119
 75: 1.0021