The forces holding diiodine molecules in the crystal are modest, and liquid iodine is not stable at ordinary temperatures and pressures, so that solid iodine sublimes to give a rather large concentration of diatomic molecules in the vapor phase. (religion-online.org)
It's available 24/7 and cheaper than paying a tutor by Spectroscopy - Energy states of real diatomic molecules: For any real molecule, absolute separation of the different motions is seldom encountered since (myintimcity.com)
Molecules like N2 and O2 (99 % of Earth's atmosphere) can't absorb longwave radiation because identical diatomic molecules don't bend (they are symmetric). (theinconvenientskeptic.com)