Echelle spectra recorded at the Li I λ6707 line are reported for 19 main-sequence members of NGC 752, an open cluster approximately 2.5 times older than the Hyades. The spectral types of the stars range from about F2 at the turnoff point to about K1. The variation of the atmospheric Li/H ratio with effective temperature shows three principal features. (1) A sharp decline of the lithium abundance toward cooler temperatures is more pronounced than in the Hyades. (2) The initial cluster lithium abundance estimated from the asymptotic region defined by four of the five stars nearest the turnoff is Li/H ≈ 1×10-9. (3) Four stars in a very narrow temperature range centered near 6600K show a deficiency of atmospheric lithium which ranges up to a factor of more than 30 compared to slightly hotter or cooler stars.
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Hobbs et al. (1986) studied this question.