When they reach the axis that the laser pulse is traveling along, they overshoot and end up traveling outward again, producing a wavelike oscillation[ see box on preceding page].

• 当电子到了雷射脉冲所经过的轴，就会再次受到轰击，而再次向外运动，产生如波动般的震盪（前页〈电子泡泡里〉。