N2 Buffer Gas Research Articles

Investigation of the fluorescence of molecular iodine in the 340 nm band

Results are presented of observations of the fluorescence of iodine vapor, subjected to cw optical pumping, as a function of the temperature and pressure of the SF6, N2, Ar, Xe, He, and Kr buffer gases. It is shown that an increase of the fluorescence in the 340 nm band with rising buffer gas pressure is accompanied by a decrease in the iodine fluorescence in the 250–330 nm band. The efficiency of the action of the buffer gas depends on its molecular weight and on the wavelength of the exciting light. The intensity depends on the buffer gas used. An estimate is made of the rate of quenching of the fluorescence by iodine molecules in the ground state kqτ =(3.0±0.30)×10−18 cm3. For Xe, kqτ = (1.2±0.6)×10−18 cm3. It is shown that the fluorescence quantum efficiency η does not depend on the mixture temperature up to 425 °C. The value of η for optical pumping (λ = 190 nm) of a mixture of iodine vapor and 5 atm SF6 is η = 0.04±0.02 and for a mixture with 1.5 atm Ar, is η = 0.05±0.02.

Saturable absorber overlap of iodine 127 with the optically pumped 546-nm mercury laser

A single isolated saturated-absorption feature in 127I2 using the optically pumped 546.1-nm Hg laser has been observed with low (∼6 MHz) resolution. The 3S1→3P2 Hg laser transition can be centered exactly on this feature by varying the N2 buffer gas pressure using the measured pressure tuning rate of −9.4 MHz/Torr. This may provide an attractive laser system for absolute wavelength stabilization.

Rate constants for the reaction of CH3 with N2F4 and NF2

The rate constants for the following reactions have been determined by mass spectrometric measurements following flash photolysis of CH3I/N2F4/(NF2)/N2 gas mixtures: CH3 + N2F4 → CH3NF2 + NF2, k1 = 6.7 ± 0.8 × 10−12 cc/molecule · sec (1), and CH3 + NF2(+M) → CH3NF2, k2 = 2.0 ± 1.1 × 10−12 cc/molecule · sec (2). The measurements were made near room temperature (40 °C) with sufficient N2 buffer gas to insure that only ground-state methyl radicals were reacting. Changes in the buffer-gas pressure did not change the observed second-order rate constant k2. This result is consistent with the rapid HF elimination from CH3NF2 that has been estimated for Reaction (2).

Spin relaxation in an optically oriented sodium vapor

The spin relaxation times of an optically oriented Na vapor diffusing in buffer gases of He, H2, and N2 have been measured, and from these times the spin disorientation cross-sections of atomic Na colliding with He, H2, and N2, and the mutual diffusion constants for Na in these gases have been determined. The spin relaxation times of a Na vapor in mixtures of He and dilute amounts of A, Kr, and Xe have been measured and the spin disorientation cross-sections for Na colliding with A, Kr. and Xe have been determined. In an Appendix, the relaxation time of Na in He is used to set an upper limit on the nuclear electric dipole moment of23Na.