Ab initio configuration interaction calculations using effective core potentials are presented for the low‐lying electronic states of HgCl and HgBr. The B→X laser wavelengths and vibrational constants for the B and X states are in very good agreement with experiment. The equilibrium separations (Re) for the B and X states in HgCl (HgBr) are found to be 2.42 (2.61 A) and 2.93 A (3.04 A), respectively. The purely electronic radiative lifetime for the B state in HgCl (HgBr) is calculated to be 27.5 ns (27.6 ns). The mixing of ionic and covalent character in the X and B states and its effect on the R dependence of the transition moment is discussed briefly. Finally, the possibility of self‐absorption is considered.

The electronic structure of HgCl and HgBr

Geometrical considerations are important with respect to the stability and efficiency of avalanche electric discharge lasers. Parameters such as the electrode contours and the distribution of preionization electrons affect excitation rates through the relative values of the local electric field, local depletion of initial species, and through the response of the discharge circuitry to spatially dependent conditions within the plasma. Constriction of the discharge and subsequent impedance mismatch of the discharge to the pulse forming line result from these spatial nonuniformities. In this paper geometrical effects in the mercury bromide electric discharge laser are examined by comparing the results from a multidimensional discharge and kinetics model with experimental observations. The code models electron and heavy particle kinetics and laser intensity in time and one spatial dimension: parallel to the electrodes and perpendicular to the optical axis. Quantities whose spatial dependence is perpendicular ...

Multidimensional modeling of transverse avalanche laser discharges: Applications to the HgBr laser

The dissociative excitation of HgBr2 by rare‐gas metastable atoms and N2(A3J+u) has been studied in a flowing afterglow apparatus. Reaction of HgBr2 with the lighter rare gas (He, Ne, and Ar) metastable atoms gave strong Hg* line emissions. Intense HgBr (B2J+→X2J+) emission (300–513 nm) from Xe(3P2) and N2(A) reactions was observed. The rate constants for HgBr* (B) formation from HgBr2 excitation by Xe(3P2) and N2(A) were determined as (5.31.5) ×10−10 cm3 sec−1 and ⩽1×10−10 cm3 sec−1 at 350 °K, respectively. Also, the formation rate constant for HgBr* (C) from HgBr2+Xe(3P2) was determined to be (1.10.3) ×10−10 cm3 sec−1.

Dissociative excitation of HgBr2 by rare‐gas metastable atoms and N2(A 3σ+u)

Tunable laser, infrared fluorescence techniques are used to study the detailed photodissociation dynamics of the linear triatomic molecule HgI2. The quantum yield of excited I(5 2P1/2) atoms has been measured in the first long wavelength absorption band of HgI2 from 265 to 320 nm. From quantitative measurements of the yield of excited I atoms, it is shown that the total absorption cross section in this region is actually composed of two distinct components. These components correspond to states leading to both excited and ground state I atoms according to the processes HgI2→HgI+I or I*. From the time decay of the excited I* atoms as a function of HgI2 pressure, the collisional deactivation rate of I* by the parent HgI2 molecule has been obtained. This quenching rate constant is 4.5±0.2×10−10 cm3 molecule−1 s−1 at T=453 K, which is essentially a gas kinetic rate.

Tunable laser photodissociation of HgI2: Quantum yield for formation of excited I(5 2P1/2) atoms

Photolytic pumping of the HgCl35(B→X) laser has been demonstrated. Oscillation at 557.6 and 558.4 nm was obtained by irradiating HgCl2 vapor and helium with incoherent Xe*2 emission at 172 nm from an e‐beam‐excited xenon plasma. Also, by photodissociating HgCl2 with ArCl* (175 nm) fluorescence, the HgCl(B) state radiative lifetime was determined to be 22.2±1.5 ns.

vuv‐pumped HgCl laser

Lasing action was achieved on the B2Σ+ → X2Σ+ transition of HgBr by dissociating HgBr2 vapor by electron collision in a transverse electric discharge. The lasing wavelengths, consisting of six lines between 502 and 505 nm, are identical with the ones previously measured by excitation through photodissociation.

J. E. Celto

Papers

Mercuric bromide dissociation laser in an electric discharge

Mercuric bromide dissociation laser in an electric discharge