The helium singlet 1s4d-1s2p line (492.2 nm) has been measured in a corona discharge done in liquid helium at 4.2 K. A significant shift towards the blue direction is visible on the spectrum. Using an empirical model for the He-He* potential energy difference, we have performed a fitting of the line shape. The best-fit result is in good agreement with the experimental spectrum. It is shown that the blue shift is determined by the maximum of the potential energy difference function. Based on the fitting results, we give an estimate of this quantity.

中文翻译：

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液体电晕放电中氦492.2 nm线上蓝移的测量和分析

氦单重态1s4d-1s2p线（492.2 nm）已在4.2 K的液氦中进行的电晕放电中测量。在光谱上可以看到向蓝色方向的明显偏移。使用He-He *势能差的经验模型，我们进行了线形拟合。最佳拟合结果与实验光谱非常吻合。结果表明，蓝移由势能差函数的最大值确定。根据拟合结果，我们对该数量进行估算。