In the case of nitrosobenzene itself, the metastable monomeric form could be prepared by sublimation onto a cold finger. The monomeric material is selectively sublimed due to its lower molecular weight and is collected on a cold finger as lustrous, dark green crystals.
For nitrosobenzene, the metastable monomeric form can be obtained through sublimation onto a chilled surface. This process preferentially isolates the lighter monomer due to its lower molecular weight, which then crystallizes on the cold finger as lustrous, dark green crystals.