Analysis of the naphthalene vapour absorption bands at 3200Å. I. Naphthalene h -8

Abstract

The absorption bands of naphthalene vapour near 3200 A have been measured at medium and high resolution and analyzed for the first time. The bands have strong heads weakly degraded to the red. The direction of polarization of the 0—0 pure electronic transition has been identified from the band contour of the corresponding band, which shows a single intense maximum. Calculations of rotational energy levels confirm that this is a quasi-parallel A -type band of the asymmetric rotor, with polarization along the longer in-plane molecular axis. Accompanying the electronically allowed band is a set of stronger vibrationally induced bands, which show doubled intensity maxima. From approximate calculations of contours it is confirmed that these are quasi-perpendicular B -type bands, polarized along the shorter in-plane axis. The electronic assignment B 2u <- A g , long-axis polarized, agrees with McClure’s assignment from the spectrum of naphthalene embedded in durene crystals. The use of rotational band contours for assigning transitions is novel in larger molecules and seems likely to be applicable rather widely. A hitherto unrecorded ground-state frequency 506 cm<super>-1</super> of species b 3g has been identified, and a number of other ground and excited-state frequencies confirmed and assigned, or recorded for the first time.

Spectroscopic Properties of Naphthalene on the Surface of Ice Grains Revisited: A Combined Experimental–Computational Approach

“…The naphthalene 0–0 transition was reported to be very insensitive to solvents (314.9 nm in hexane , and ethanol) and phase change (312.3 nm in the gas phase; − 317.7 and 316.2 nm in crystals ,,, ). No substantial shift in the excitation spectrum of 1-methylnaphthalene was observed in/on the ice surface, and therefore it would be surprising to see any larger band shift after freezing naphthalene solutions.…”

“…Our spectroscopic and computational analyses of naphthalene in frozen aqueous solutions show a negligible shift of the excitation/absorption energies with respect to those of the liquid and gas phases (Table 3). The results of the experiments are discussed in the following text to justify this finding.The naphthalene 0-0 transition was reported to be very insensitive to solvents (314.9 nm in hexane47,48 and ethanol 54 ) and phase change (312.3 nm in the gas phase; 47-49 317.7 and 316.2 nm in crystals50,51,53,94 ). No substantial shift in the excitation spectrum of 1-methylnaphalene was…”

Stability and Reactivity of Aromatic Radical Anions in Solution with Relevance to Birch Reduction

“…This can be understood by inspection of the nodal pattern in the HOMO and LUMO orbitals shown in Figure S12 in the SI. The change in the bonding pattern is sufficient to give a long Franck–Condon progression in the electronic absorption spectrum in the totally symmetric C–C framework stretching modes. , …”

“…The change in the bonding pattern is sufficient to give a long Franck−Condon progression in the electronic absorption spectrum in the totally symmetric C−C framework stretching modes. 80,81 Upon removal of a SOMO π* electron from the molecular anion, one would expect an oppositely signed bond alternation change, but not as dramatic in magnitude because an electron has not been changed in the π HOMO. Gas-phase highresolution PE spectra of anthracene radical anion (Ant − ) report 82 detachment to the singlet and triplet states on an equal footing, as is seen in our work.…”

David Parker Craig AO FAA. 23 December 1919—1 July 2015

“…On the spectroscopic side, he began with the molecule naphthalene in the gas phase, together with M. F. Redies, an MSc student. This laid the foundation for work that later resumed in London on a much more powerful spectrograph, which resulted in the first analysis of the weak naphthalene system at 320 nm (25, 28) and was also the precursor of studies on the crystal spectrum of this molecule (23,26). On the theoretical side, particularly with J. R. Walsh and E. A. Magnusson, David turned to the calculation of the spectra of molecular crystals (20) and to some ideas on valence theory, focusing on the new concept of 'orbital contraction' (18,19,21,22).…”