With the degenerate ground states by the competition between the interacting energies and geometrical properties of the crystal lattice at a specific given site, the geometrically frustrated magnetism has attracted a lot of attention in the past decades. One exotic state is quantum spin liquid (QSL) state in which spins cannot find a stable/exclusive ordering state and are quantum entangled over long distances, but do not show magnetic order even in the zero-temperature limit Recently we have discovered new QSL behavior in NaReCh2 (Re=rare earth, Ch2=O, S, Se) and here we propose to measure the crystal electronic field (CEF) excitations of NaErSe2 and NaYbSe2 to understand the role of single ion anisotropy and origin of the quantum spin liquid behavior using MERLIN.