Infrared spectra of $N2O–(ortho-D2)N$ and $N2O–(HD)N$ clusters trapped in bulk solid parahydrogen

High-resolution infrared spectra of the clusters $N2O–(ortho-D2)N$ and $N2O–(HD)N$⁠, $N=1–4$⁠, isolated in bulk solid parahydrogen at liquid helium temperatures are studied in the $2225cm−1$ region of the $ν3$ antisymmetric stretch of $N2O$⁠. The clusters form during vapor deposition of separate gas streams of a precooled hydrogen mixture (⁠$ortho-D2∕para-H2$ or $HD∕para-H2$⁠) and $N2O$ onto a $BaF2$ optical substrate held at $∼2.5K$ in a sample-in-vacuum liquid helium cryostat. The cluster spectra reveal the $N2O$ $ν3$ vibrational frequency shifts to higher energy as a function of $N$⁠, and the shifts are larger for $ortho-D2$ compared to HD. These vibrational shifts result from the reduced translational zero-point energy for $N2O$ solvated by the heavier hydrogen isotopomers. These spectra allow the $N=0$ peak at $2221.634cm−1$⁠, corresponding to the $ν3$ vibrational frequency of $N2O$ isolated in pure solid parahydrogen, to be assigned. The intensity of the $N=0$ absorption feature displays a strong temperature dependence, suggesting that significant structural changes occur in the parahydrogen solvation environment of $N2O$ in the $1.8–4.9K$ temperature range studied.