The high-resolution infrared spectrum of the ν11 band of allene-d4

The infrared band ν₁₁ around 300 cm^?1 of allene-d₄ has been studied at a resolution of 0.010 cm^?1. The J structure in the central Q branches of this perpendicular band was resolved and P- and R-lines were assigned to subbands with {K″} ≦ 18. A ground-state analysis resulted in B₀ = 0.232187(30) cm^?1, D₀^J = 6.3(1.0) × 10^?8cm^?1, and D₀^JK = 3.0(4) × 10^?6cm^?1. Upper-state constants including η₁₁^J and η₁₁^K were derived. Special attention was paid to the study of l-type doublings. Doublets due to q^(?)-doubling were resolved and accordingly the value q₁₁^(?) = ?0.000160(3) cm^?1 was derived. The more usual q⁽⁺⁾-doubling was also observed, and the result q₁₁⁽⁺⁾ = 0.000144(4) cm^?1 was obtained.