Sample

IR spectrum α-form (cm⁻¹)

IR spectrum β-form (cm⁻¹)

Direct transitions (eV)

Indirect transitions (eV)

SMA

(KBr pellets)

720

735, 783

-

-

SMA

(thin films)

721

732, 785

3.1

2.0

SMB

(KBr pellets)

721

730

-

-

SMB

(thin films)

-

-

1.4

1.2

SMC

(KBr pellets)

720

735, 781

-

-

SMC

(thin film)

717

732, 780

2.5, 2.6

2.4, 2.6

SMD

(KBr pellets)

721

779

-

-

SMD

(thin film)

-

-

1.3, 1.7, 3.1

1.4, 1.5, 2.3