Liddel and Scott
Greek Lexicon

ἆ, exclamation expressing pity, envy, contempt, etc., in Hom. always ἆ δειλέ, ἆ δειλώ, ἆ δειλοί, Il. 11.441, 17.443, Od. 20.351, cf. Thgn. 351, Theoc. Ep. 6; also in Lyr., Archil. 135, and Trag., A. Ag. 1087, etc.; in reproofs or warnings, ἆ, μηδαμῶς . . S. Ph. 1300, cf. OT 1147, E. Hel. 445, etc.:—freq. with adj., ἆ μάκαρ Thgn. 1013, Choeril. 1; ἆ τάλας Semon. 7.76, cf. B. 15.30; ἆ τρισευδαίμων Id. 3.10; rarely alone, Ar. Ra. 759; sts. doubled, ἆ ἆ A. Pr. 114, 566, Ar. V. 1379. —Rare in Prose, Pl. Hp.Ma. 295a (Euclusap.Sch. ad loc. is said to have used it = νῦν).