For giants in the Hertzsprung gap, the relations between Teff, v sin i, and lithium surface abundances are reinvestigated and compared with the relations found for Hyades main-sequence F stars. For the Hyades main-sequence F stars, the v sin i decrease steeply around Teff ~ 6450 K. At the same temperature the lithium surface abundances show a narrow, deep dip. For most giants there is also a steep decrease of v sin i for Teff around 6450 K. At this temperature the lithium surface abundances of the giants also decrease steeply and remain low for Teff < 6400 K. The changes in rotation and Li surface abundances occur over a temperature interval of less than 300 K, which for a 2 M⊙ giant corresponds to an age interval of about 106 yr. The simultaneous steep decreases of rotation velocities and Li surface abundances indicate that for the giants these changes are due to the same cause, which we suggest to be deep mixing. It then seems rather likely that for the Hyades main-sequence F5 V stars the decrease of rotation and Li surface abundance is also caused by deep mixing. We suggest that in both cases the changes are related to the merging of the hydrogen and helium convection zones.
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机译：对于Hertzsprung间隙中的巨星，将重新研究Teff，v sin i和锂表面丰度之间的关系，并将其与Hyades主序列F星的关系进行比较。对于Hyades主序列F星，v sin i在Teff〜6450 K附近急剧下降。在相同温度下，锂表面丰度显示出狭窄的深谷。对于大多数巨头，Teff的v sin i也在6450 K附近急剧下降。在此温度下，巨头的锂表面丰度也急剧下降，并且对于Teff <6400 K而言，锂表面丰度保持较低。旋转和Li表面丰度发生变化在小于300 K的温度区间内，对于一个2M⊙的巨星来说，对应的年龄区间约为106年。旋转速度和锂表面丰度的同时急剧下降表明，对于巨人来说，这些变化是由于相同的原因引起的，我们建议进行深度混合。对于Hyades主序列F5 V星，似乎很可能是由于深度混合而导致旋转降低和Li表面丰度降低。我们建议，在两种情况下，变化都与氢和氦对流区的合并有关。
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