Table 1.

Predicted frequencies from different theoretical approaches as discussed in the text.^[a]

Mode	Theory				Experiment
	VPT2[b]	6d+6d[c]	Double Harmonic[c]		He droplets[c]	Gas phase[d]
	ν [cm−1]	ν [cm−1]	ν [cm−1]	μ⊥:μ∥	ν [cm−1]	ν [cm−1]
(DT)	85	89	126.7	100:0	86	52.9, 87.7
(AW)	121	109	149.6	27:73	99	97.9, 107.9
					107–120	110.0, 112.4
(AT)	122	109	139.8	99:1	108–118	109.0
					126–138
(OO)	144	152	181.5	24:76	–	142
(DT)2	–	181	–	–	185	142
(IPL)	304	300	351.2	90:10	283, 296	–
(OPL)	495	500	609.6	100:0	492, 503	524

[a] The normalized parallel and perpendicular components of the transition dipole moment obtained from double harmonic calculations are shown, as are results from experimental studies. [b] From Ref.  ^[46] . [c] This work. [d] From Ref. [ ²⁹ , ³¹ , ⁴³ , ⁴⁴ , ⁴⁵ ].