Analysis of the naphthalene vapour absorption bands at 3200 A. II. Naphthalene d -8

The absorption spectrum of octadeuteronaphthalene near 3200 Å has been measured and partially analyzed. The origin is at 32138.2 cm-1, 118 cm-1 higher than that of naphthalene h-8. The analysis of the spectrum shows a nearly complete similarity to naphthalene h-8, with differences only in the relative ability of non-totally symmetrical vibrations to induce absorption along the shorter in-plane molecular axis. In naphthalene this ability is largely confined to two b3g vibrations of 438 cm-1 and 911 cm-1 in the upper state; in naphthalene d-8 the b3g vibration of 422 cm-1 behaves analogously to 438 cm-1 and induces the strongest bands in the system, but there are several higher b3g frequencies giving false origins, indicating important changes in the vibrational modes on deuteration. As in naphthalene, long-axis polarized bands show single maxima and short-axis polarized bands two maxima spaced by 2 to 3 cm-1. The band group with principal head 490 cm-1 below the origin shows a structure unique in the whole system: it is proposed that this is due to Coriolis coupling of the ag fundamental 493 cm-1 to a newly identified b3g fundamental 490 cm-1. Several upper-state fundamentals are reported for the first time.