Potential energy surface Pulse method

The second example is the quadratically chirped pump-dump scheme. Since the pioneering work by Tannor and Rice [119], the pump-dump method has been widely used to control various processes. However, since it is not possible to transfer a wave packet from one potential energy surface to another nearly completely by using the ordinary transform limited or linear chirped pulses, the... 

An intuitive method for controlling the motion of a wave packet is to use a pair of pump-probe laser pulses, as shown in Fig. 13. This method is called the pump-dump control scenario, in which the probe is a controlling pulse that is used to create a desired product of a chemical reaction. The controlling pulse is applied to the system just at the time when the wave packet on the excited state potential energy surface has propagated to the position of the desired reaction product on the ground state surface. In this scenario the control parameter is the delay time r. This type of control scheme is sometimes referred to as the Tannor-Rice model. 

In this sense, the control of electronic transitions of wavepackets using short quadratically chirped laser pulses of moderate intensity is a very promising method, for two reasons. First, only information about the local properties of the potential energy surface and the dipole moment is required to calculate the laser pulse parameters. Second, this method has been demonstrated to be quite stable against variations in pulse parameters and wavepacket broadening. However, controlling of some types of excitation processes, such as bond-selective photodissociation and chemical reaction, requires the control of wavepacket motion on adiabatic potential surfaces before and/or after the localized wavepacket is made to jump between the two adiabatic potential energy surfaces. 

Early semiempirical calculations laid the foundations for subsequent ab initio methods which can now not only describe the electronic structure of optically accessible excited states, but also model the wavepacket propagation on the resulting potential energy surfaces. These models are supported by ultrafast studies using femptosecond (fs) pulsed lasers with a variety of detection systems. Many systems use indirect detection of excited-state processes because many excited states are unbound and not amenable to spectroscopic techniques. 

Fig. 1.1. Principles of the real-time multiphoton ionization (MPI) (a) and NeNePo (b) spectroscopic technique, (a) Principle of time-resolved MPI spectroscopy. A wave packet is prepared in an excited state of the neutral system by a pump pulse. Since in general the transition probability to the ion state is a function of the wave packet s location on the potential-energy surface, the propagation of the wave packet can be probed by a second, time-delayed pulse, (b) Principle of the time-resolved NeNePo process. Starting in the anion s potential-energy surface, an ultrashort pump pulse detaches an electron cuid prepares a wave packet in the neutrcd. After a certain delay time At a probe pulse photoionizes the neutral. The time-dependent signal of the cation s intensity is detected. For convenience, this method is called NeNePo , Negative-to-Neutrcd-to-Positive...

Fig. 2.25. Principle of the NeNePo process. Beginning at the anion s potential-energy surface, an ultrashort pump pulse detaches an electron and prepares a wave packet in the neutral. After a certain delay time At a probe pulse photoion-izes the neutral. The method is named NeNePo , since the overall process is a Negative-to-Neutral-to-Positive charge reversal transition...

Besides the traditional capacitance versus voltage (C/V) measurements, which are mainly used for the characterisation of MOS and EIS capacitances, the scanned light pulse technique (SLPT) was introduced by Engstrom and Aim [13], first for MOS structures. This technique utilises a fight source to illuminate a local area of the MOS structure. Thus, a local photo-effect-induced current can be measured, which only depends on the local properties and energy states of the illuminated region of the MOS structure. In 1988, Hafeman et al. combined this SLPT method with EIS structures to develop the LAPS [14,15]. This sensor is capable of measuring the surface potential of the electrolyte-transducer interface with a lateral resolution. Hence, the surface... 

Radiation grafting [83, 84, 85, 86, 87, 88, 89] is a very versatile and widely used technique by which surface properties of almost all polymers can be tailored through the choice of different functional monomers. It covers potential applications of industrial interest and particularly for achieving desired chemical and physical properties of polymeric materials. In this method, the most commonly used radiation sources are high-energy electrons, y-radiation, X-rays, U.V.-Vis radiation and, more recently, pulsed laser [90], infrared [91], microwave [92] and ultrasonic radiation [93]. Grafting is performed either by pre-irradiation or simultaneous irradiation techniques [94, 95]. In the former technique, free radicals are trapped in the inert atmosphere in the polymer matrix and later on the monomer is introduced into... 

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