Visualization of atomic and molecule excitation/ionization processes with ultra-short (attosecond) and optical gated (femtosecond) laser pulses and study of high harmonic generation (HHG) in a filament

使用超短（阿秒）和光门控（飞秒）激光脉冲可视化原子和分子激发/电离过程，并研究灯丝中的高次谐波产生 (HHG)

基本信息

批准号：
RGPIN-2017-06181
负责人：
Witzel, Bernd
金额：
$ 1.53万
依托单位：
Université Laval
依托单位国家：
加拿大
项目类别：
Discovery Grants Program - Individual
财政年份：
2018
资助国家：
加拿大
起止时间：
2018-01-01 至 2019-12-31
项目状态：
已结题

来源：
https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=668751
关键词：
Visualization atomic molecule excitation ionization

项目摘要

In the past year, we have been able to generate with our Femtolaser V system (800 nm, 5 mJ, 1 kHz, CEP stabilized) high harmonic spectra up to 130 eV pulses in a filament created in a differential pumped gas cell. We plan to extend this region with our TOPAS system. We have already measured CEP (carrier envelope phase) stabilized laser pulses of 2400 nm up to 1mJ. The setup will allow us to extend the HHG cut-off region up to 400 eV.****The scientific goals are divided into 3 different axes.****In a first project we want to study excitation processes and inner-shell ionization as well as inner shell excitation processes of molecules and atoms.****Therefore we will use (femtosecond) pump - (sub-femtosecond) probe experiments and measure the electron spectrum of both laser pulses together. We will obtain in the low energy part of the electron spectrum the ATI (above threshold ionization) spectrum of the femtosecond pump laser, the high energy part will measure the probe pulse. We are only limited to laser intensities where the energy distribution of electrons from the ATI-spectrum does not overlap the electron energy spectrum from the probe pulse. This restriction can be overcome when the momentum distribution from the electrons of the pump and probe pulse is different. We want to upgrade our VMI (velocity map imaging) spectrometer to measure both contributions. With this technique we will be able to study inner-shell ionization, inner shell excitation processes of molecules and atoms. This offers us complementary information to HHG experiments.****In a second project we want to visualize processes taking place in a sub cycle of a laser.****We have started atom ionization/excitation experiments with polarization gated laser pulses and have been the first to publish VMI electron spectra. These laser pulses are composed of circularly polarized sections at the leading and trailing edges of the pulse and of an experimentally defined linearly polarized central part. The central part can be restricted down to a fraction of an optical cycle. Processes taking place only at linear polarization can be restricted in time down to a half cycle. We want to use this method for different wavelengths as well as ionization processes with laser pulses with sub-cycle linear polarization.****We want to better understand HHG generation in a filament and continue the experiments we have started recently with 800 nm. Later we will extend these experiments to other wavelengths generated by the TOPAS system. There we want to study the effect of atomic/molecular resonances as well as the possibility to amplify a HHG signal in a filament. Measurements, where the intensity as well as the wavelength dependent HHG spectra are taken at the same time will be an ideal tool to visualize atom/molecular high laser field physics.*****

在过去的一年中，我们能够使用Femtolaser V系统（800 nm，5 MJ，1 kHz，CEP稳定）高谐波频谱，高达130 eV脉冲，在差异泵送燃气电池中产生的细丝中。我们计划使用我们的TOPAS系统扩展该区域。我们已经测量了CEP（载体包膜相）稳定的激光脉冲，为2400 nm至1MJ。该设置将使我们能够将HHG截止区域扩展到400 eV。****科学目标分为3个不同的轴。 ****因此，我们将使用（飞秒）泵 - （次秒）探针实验并测量两种激光脉冲的电子光谱，将分子和原子的内壳激发过程。我们将在电子光谱的低能部分中获得飞秒泵激光器的ATI（高于阈值电离）频谱，高能部分将测量探针脉冲。我们仅限于激光强度，在激光强度中，来自ATI光谱的电子的能量分布不会与探针脉冲的电子能谱重叠。当从泵的电子和探针脉冲的电子中的动量分布不同时，就可以克服这种限制。我们希望升级VMI（速度图成像）光谱仪以测量这两个贡献。通过这种技术，我们将能够研究内壳电离，分子和原子的内壳激发过程。这为我们提供了HHG实验的互补信息。****在第二个项目中，我们希望在激光的子周期中可视化过程。是第一个发布VMI电子光谱的人。这些激光脉冲由脉冲的前沿和后侧边缘和实验定义的线性极化中心部分组成。中心部分可以限制为光周期的一小部分。仅在线性极化下发生的过程才能在时间限制为半周期。我们希望将此方法用于不同的波长以及带有亚周期线性极化的激光脉冲的电离过程。稍后，我们将将这些实验扩展到TOPAS系统生成的其他波长。我们想研究原子/分子共振的效果，以及在细丝中扩增HHG信号的可能性。在同一时间进行强度和依赖性HHG光谱的测量值，将是可视化原子/分子高激光场物理的理想工具。*******************