The mercury–ammonia system at high mercury densities

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Abstract
The properties of optically excited Hg/NH3 and Hg/ND3 mixtures have been studied as a function of mercury pressure in the range 1–40 Torr. At low mercury pressures ≲1 Torr, the well-known UV emission band due to HgNH3* is dominant; this regime has been investigated extensively over the past ten years. However, at higher pressures the UV band disappears and is replaced by a strong green emission band, centered near 500 nm. From a detailed study of the spectral and temporal characteristics of the green band, it is concluded that it arises from the formation of the Hg2NH3* (or Hg2ND3*) excited molecular complex. The lifetime of this exciplex has been measured and is found to be 3.8 msec (±25%). Because of interest in the system as a potential energy storage laser medium, optical transmission measurements have been carried out at selected wavelengths. Net absorption has been observed across the green band at high mercury density, as well as in the UV band in the low density regime.