Investigation of the transition at a wavelength of 506 nm, intended for deep cooling of thulium atoms

A scheme is proposed for the third stage of laser cooling of thulium atoms at a wavelength of 506.2 nm, and a system for stabilising the laser radiation frequency is described, which provides the required characteristics. The transition |4f¹³(2F^o)6s², J = 7/2〉 → |4f¹³ × (2F ^o_7/2) 6s6p, J = 9/2〉 at a wavelength of 506.2 nm is detected in a magneto-optical trap with the employment of the developed laser setup. The value of hyperfine splitting of the transition upper level is measured, and the single-dimension cooling at this wavelength is observed for the first time.