We measure the flow regime change of C₆₀ molecular beams, produced by a Knudsen oven with an orifice (diameter, 1mm; thickness, 0.5 mm), from effusive to transitional. We determine the change temperature to be about 800 K and find an inefficient translational cooling of C₆₀ molecules in the transitional regime. Such an inefficient cooling leads us to modify the velocity distribution function assumed standardly in directed molecular beams. The determined change temperature could be used as a benchmark for estimating the beam regime in experiments involving C₆₀ molecular beams prepared by a Knudsen oven with a thin millimeter-scale orifice.

中文翻译：

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C ₆₀分子束的态变化和过渡态行为

我们测量了由Knudsen烤箱带孔（直径1mm；厚度0.5mm）从发散到过渡的C ₆₀分子束的流动状态变化。我们确定变化温度约为800 K，并发现过渡态下C ₆₀分子的转化冷却效率低下。这种低效的冷却导致我们修改了定向分子束中标准假设的速度分布函数。所确定的变化温度可以用作评估束态的基准，该实验涉及由具有窄毫米级孔的Knudsen烤箱制备的C ₆₀分子束。