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Energy pooling to the Ba 6s6p 1P10 level arrising from collisions between pairs of metastable Ba 6s5d 3DJ atoms

The energy-pooling rate coefficient for the Ba (6s5d 3DJ) + Ba (6s5d 3DJ) -> Ba (6s2 1S0) + Ba (6s6p 1P10) process has been measured. The barium atoms were excited by a cw diode laser tuned to the frequency of the 791.3 nm intercombination line and the metastable atoms in the 6s5d 3DJ state were produced due to radiative and collisional depopulation of the laser-excited 6s6p 3P01 state. The measurements were performed at 138Ba number densities of about 4x10^10 cm^(-3) and at 30 mbar argon as the buffer gas. Most of the barium ground state atoms in the excitation zone were transferred to the triplet metastable state at the laser pump power applied. The energy pooling rate coefficient was determined by comparing the fluorescence intensity of the barium 553.6 nm resonance line and the fluorescence intensity of the intercombination line 791.3 nm. In addition, the populations of the metastable atoms were probed with low intensity laser radiation from a single mode ring dye laser. The rate coefficient was found to be k = 1x10^(-10) cm^3 s^(-1) at T = 730 K.

energy pooling; cross sections; excitation transfer

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