Colliding pulse technique

As one important example, the introduction of the prism-controlled, colliding-pulse, mode-locked (CPM) dye laser [12,13] led almost immediately to developments in measurement technique with pulses of less than 100... 

The pulsed technique employed by Henchman et uses an ordinary source in which a short electron pulse provides reactant ions. Another short pulse applied to a repeller plate accelerates these to a definite energy (about 1 eV). Before emerging from the exit slit of the chamber, the reactant ions may collide with un-ionized gas to give product ions. The forward velocity of both reactant and product ions is measured by applying a variably delayed gating pulse to a deflection electrode outside of the ionization chamber. A more recent version of the apparatus incorporates separate ion production and reaction chambers, as well as a stopping potential analyzer. ... 

The shortest dye laser pulses were first obtained by Fork et al. [12]. Placing a combined prism and diffraction grating sequence into the cavity of their colliding-pulse mode-locked (CPM) dye laser, they could provide quadratic and cubic phase compensation and obtained pulses of 6fs full width half maximum (FWHM). However, the tunability of this special dye laser configuration is extremely restricted and limits the application to spectroscopic investigations rather severely. Therefore, sometimes old-fashioned and less sophisticated techniques such as the simple synchronous pumping of a dye... 

Singh, S. Short pulse generation from a flashlamp-pumped Rhodamine 6G ring dye laser using the colliding pulse mode-locking technique. Appl. Opt. 1987,26,66-69. 

In an FT-ICR instrument, fragmentation may be achieved by colliding ions with neutrals (CID) but various other strategies are available, such as collision with surfaces (surface-induced dissociation) or bombardment with ultraviolet or infrared radiation from a laser (ultraviolet photodissociation and multiphoton infrared photodissociation). Dissociation may also be achieved by the absorption of black-body radiation produced by a heated vacuum chamber walls (blackbody infrared dissociation). An advantage of these radiation-induced fragmentation methods is that gas pulses are no longer required. Sustained off-resonance irradiation is the preferred, radiation-based method for FT-ICR MS because it is the simplest to implement and tune. Very low energy and multiple excitation collisional activation techniques are also available. 

Figure 24.1 Top schematic view of the pick-up technique a molecular beam apparatus to investigate the spectroscopy and dynamics of sodium-containing clusters is shown. The metallic cluster is produced by the pick-up technique under crossed-beam conditions. Adapted with permission from Polanyi et al, J. Phys. Chem. 99 13691. Copyright 1995 American Chemical Society. Bottom schematic view of a pick-up technique based on a beam-gas arrangement. After nozzle expansion, a skimmer extracts the beam that subsequently collides with the particles in the gas cell. The cluster beam is ionized by a pulsed laser and mass analysed in a TOE mass spectrometer. Reproduced from Nahler et al, J. Chem. Phys., 2003, 119 224, with permission of the American Institute of Physics...

---