Within the frame work of Pekar's model for a spatially dispersive, bounded medium, optical spectra of thin crystals, reported by us recently, are analyzed, showing a structure due to the interference of additional waves and the Pabry-Perot structure deviating markedly from the one expected in the classical case in the neighbourhood of exciton resonances.A comparison of the experimental reflectivity with that obtained numerically provides values for all physical parameters defining dispersion and damping of the photoexcitons. Some additional experimental results for excitons in thin crystals are reported: evidence for the induced surface wave, an effect of the forbidden exciton, etc. HaK HaMM J7Xe COO6waJlOCb, I3 MHTep@epeHUMOHHbIX CIIeHTpaX TOHKMX KPII-CTaJIJIOB B OKpeCTHOCTH 3KCHTOHHbIX pe30HaHCOB IIpORBJKRIOTCfi ABa TMIIa OCO-6eHHOCTefi: CTpYKTYpa, BO3HHKaH)II~aR 113-38 MHTCpl$epeHqMII n06aBOxIHbIX BOJlH II CTpyIcTypa CDaBpn-nepo, 3HacWITeJlLH0 OTXM~aIOwaXCH OT TOB, I-iOTOpaH OifcE1.1-PYIOTCH B paMKaX MOaeJIII neKapa OrpaHH4eHKKOt CpenbK C IIpOCTpaHCTBCHHOfi naeTcx B KnaccmYecKoM cnyqae. €3 Hamoxwet3 pa6oTe ~T M cnei-FTpbI a~an113k1nncnepcneii. Cpameme s~c n e p r n~e~~a n~,~o r o EI pacqwawioro cnempa n03BOJ-ReT HafiTm ~H~Y~H M R

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New precision measurement of the J/ψ -and ψ The relative measurement accuracy has reached 4 · 10 −6 for J/ψ and 7 · 10 −6 for ψ ′ , approximately 3 times better than in the previous precise experiments.