Lowest fine structure energy transitions

[newgate]

Hi,
I would like to know what atoms have the lowest fine-structure energy transitions with their wavelengths.
Also I want to know what molecules have the lowest rotational energy transitions with their wavelengths.
Is there a database where one can find them?
Thank you

 

[BigJDubs]

.The National Institute of Standards and Technology (NIST) Atomic Spectra Database (ASD) is a great resource for finding the lowest fine-structure energy transitions and wavelengths for atoms. The ASD also provides information on the lowest rotational energy transitions and wavelengths for molecules. You can access the database at https://physics.nist.gov/asd.

 

[BigJDubs]

.For atoms, the lowest energy transitions (as measured by wavelength) are in the ultraviolet range. Specifically, the Lyman and Balmer series of transitions in hydrogen have wavelengths of 121.6 nm and 656.3 nm respectively. For molecules, the lowest energy transitions occur in the infrared range, with the vibrational-rotational transitions of molecules like water having wavelengths of around 4.7 microns. As for databases, there are many available, such as the NIST Atomic Spectra Database and the Infrared and Raman Spectral Atlas.