Direct spectroscopy of Rubidium using a narrow-line transition at 420 nm Rajnandan Choudhury Das, Samir Khan, Thilagaraj Ravi and Kanhaiya Pandey Eur. Phys. J. D, 78 4 (2024) 40 Published online: 04 April 2024 DOI: 10.1140/epjd/s10053-024-00831-9