Lyman-Birge-Hopfield bands

Fig. V-9. Energy level diagram of N2. D,((N—N) = 9.76 eV L-B-H, Lyman-Birge-Hopfield bands V-K, Vegard-Kaplan bands 1, first positive bands 2, second positive bands. From Gaydon (8), p. 188, reprinted by permission of Associated Book Publishers Ltd.

The photodissociation of the most abundant gas in the atmosphere plays very little role in atmospheric chemistry below 100 km because the absorption of dissociating radiation by N2 is very weak. However, production of atomic nitrogen from N2 photolysis via predissociation does occur following absorption into the Lyman-Birge-Hopfield bands... 

B n,-A St system of N2. It has been shown that weaker infra-red bands of the B S r-B II, system, and far ultraviolet bands of the Lyman-Birge-Hopfield a IIp-X SJ magnetic dipole transition and the forbidden a system are also present in the afterglow... 

The application of two-photon spectroscopy to molecules has brought a wealth of new insight to excited molecular states. One example is the two-photon excitation of CO in the fourth positive system A TJ Ug and of N2 in the Lyman-Birge-Hopfield system with a narrow-band pulsed frequency-doubled dye laser. Doppler-free spectra of states with excitation energies between 8-12 eV can be measured with this technique [253]. 

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