Institute for Lasers, Life and Biophotonics, VU University Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
Phys Chem Chem Phys. 2012 Jul 21;14(27):9630-5. doi: 10.1039/c2cp40822h. Epub 2012 May 31.
Velocity map imaging inside an electrostatic quadrupole guide is demonstrated. By switching the voltages that are applied to the rods, the quadrupole can be used for guiding Stark decelerated molecules and for extracting the ions. The extraction field is homogeneous along the axis of the quadrupole, while it defocuses the ions in the direction perpendicular to both the axis of the quadrupole and the axis of the ion optics. To compensate for this astigmatism, a series of planar electrodes with horizontal and vertical slits is used. A velocity resolution of 35 m s(-1) is obtained. It is shown that signal due to thermal background can be eliminated, resulting in the detection of slow molecules with an increased signal-to-noise ratio. As an illustration of the resolving power we have used the velocity map imaging system to characterize the phase-space distribution of a Stark decelerated ammonia beam.
静电四极导向器内部的速度成像得到了展示。通过切换施加在棒上的电压，四极可以用于引导斯塔克减速分子和提取离子。提取场在四极的轴向上是均匀的，而在垂直于四极轴和离子光学轴的方向上使离子散焦。为了补偿这种像散，使用了一系列带有水平和垂直狭缝的平面电极。得到了 35 m s(-1) 的速度分辨率。结果表明，可以消除由于热背景而产生的信号，从而以更高的信噪比检测到慢分子。作为分辨率的说明，我们使用速度成像系统来描述斯塔克减速氨束的相空间分布。
