A device that generates low-energy x rays at the tip of a needle-like probe was developed for stereotactic interstitial radiosurgery. Electrons from a small thermionic gun are accelerated to a final energy of up to 40 keV and directed along a 3 mm outside diameter drift tube to a thin Au target, where the beam size is approximately 0.3 mm. All high-voltage electronics are in the probe housing, connected by low-voltage cable to a battery-operated control box. X-ray output, which is nearly isotropic, consists of a bremsstrahlung spectrum and several lines between 7 and 14 keV, with characteristic radiation contributing 15% of the total energy output. To date, 14 patients with metastatic brain tumors have been treated with this device.

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Flow-tube experiments on vibrational energy transfer from Nz* to CO and NO are described. A primary tlow of N z was vibrationally excited by an S-band microwave discharge and mixed with either cold CO or NO. The first overtone band radiation from the heteronuclear molecules was spectrally resolved at selected downstream stations, and the data were compared with an analytical model computed for different number density distributions. Flow-tube measurements of rotationally cold, but vibrationally excited, Nz*-CO and Nz*-NO systems indicate that at steady-state conditions, (1) the CO and NO are not in vibrational equilibrium, and (2) the nonequilibrium popUlations of the molecules cannot be predicted by the model postulated by Treanor et al.

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