The experimental lines were reported by
(1) M. Izuka, S. Yamamoto, and S. Saito, 1996, J. Chem. Phys. 105, 4923.
The predictions should be sufficient for astronomical observations. Predictions were limited to K_a ≤ 5; they should be viewed with caution above 500 GHz and throughout for K_a = 5.
Spin-statistics matter for the intensities. The nuclear spin-weight ratio is 3 : 1 for ortho-H₂CSi : para-H₂CSi. The ortho states are described by K_a odd, the para states by K_a even.
The dipole moment is from an ab initio calculation by
(2) H. S. P. Müller and D. E. Woon, 2013, J. Phys. Chem. A 117, 13868.
Please note that this value is considerably smaller than the one mentioned in (1). Vibrational effects on the dipole moment may be non-negligible because of the small value.