A.A. RUTH, A. DRAGOMIR and D.N. NIKOGOSYAN

For the first time, the four- and two-photon absorption cross-section values (s₄ = (9 ± 7) ¥ 10^-123 cm⁸ s³ /mol and s₂ = (2.5 ± 1.2) ¥ 10-55 cm⁴ s /mol) were obtained for naphthalene vapour. The determination of the four-photon absorption cross-section value is believed to be the first ever measurement of this subtle effect in a molecular gas.