Ultrafast laser molecule interaction, control and imaging of molecules with femtosecond laser pulses

该计划将围绕库仑爆炸技术(库仑成像)建立。这种方法使用激光的强场快速连续地从分子中移除许多电子，分子被还原为原子离子，然后通过库仑力相互排斥并飞离。我们将使用时间和位置敏感检测来检测所有这些碎片离子并重建分子的几何结构。为了最好地代表分子，有必要在最短的时间内从分子中移除尽可能多的电子，因此，作为计划的一部分，我们将继续开发和寻找尽可能短的脉冲，以及可用的最高强度。库仑成像的一个非常重要的应用是研究分子在激发或解离过程中几何结构的变化。我们的目标是首次成像分子在非解离激发过程中的形状变化。与追求库仑成像过程密切相关的是对小分子中的电离和解离机制的研究。在这里，我们将利用我们的设备的能力来完成分子解体的测量，试图区分电离过程中的不同路径，我们将绘制随着分子分裂而变化的电离变化方式。最后，我们的目标是使用两个能量随时间变化的激光脉冲来控制分子的振动状态，使它们的能量差始终等于增加振动能级所需的能量。这被称为拉曼啁啾绝热通道或RCAP。这种方法可能能够将高比例的分子振动群体转移到特定的水平。我们预计我们可能能够用库仑爆炸方法来成像这些振动分子。该项目的最后一部分将在蒙特利尔附近的高级激光光源进行。

The program will be built around the Coulomb explosion technique (Coulomb imaging) this method uses the intense field of a laser to remove many electrons from a molecule in rapid succession, the atomic ions which the molecule is reduced to then repel each other with Coulombs force and fly apart. We will use time and position sensitive detection to detect all of these fragment ions and reconstructing the geometry of the molecule.  In order to make the best representation of a molecule it is necessary to remove as many electrons from the molecule in the shortest time, therefore as part of the program we will continue to develop and seek out the shortest pulses possible, with the highest intensity available.  One very important application of Coulomb imaging is to study the changing geometry of a molecule during an excitation or dissociation. We will aim to image the changing shape of molecules during a non dissociating excitation for the first time.Closely related to the pursuit of the Coulomb imaging process is a study of the ionization and dissociation mechanisms in small molecules.  Here we will use the capabilities of our apparatus to make complete measurements of molecular disintegration, to try to distinguish different pathways in the ionization process, we will map the way ionization changes as the molecule breaks apart.Finally we will aim to control the vibrational state of a molecule using two laser pulses which have energies varying in time such that the difference in their energies is always equal to the energy needed to increase the vibrational level. This is known as Raman chirped adiabatic passage or RCAP.  This method might be able to transfer a high proportion of a molecules vibration population to a specific level.  We expect that we might be able to image these vibrating molecules with a Coulomb explosion method.  This last part of the project will take place at the Advanced Laser Light Source near Montreal.