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:  1447.85
nu3: ~1390
nu7:  1036.26
nu4:   907.72
nu8:   354.33

300: 1.5432
225: 1.2524
180: 1.1304
150: 1.0706
120: 1.0292
100: 1.0123
 75: 1.0022