Ionization three-photon

Fig. 1. Two-color 3-photon ionization scheme. Fig. 2. Three-photon ionization photoelectron CHD is excited by a Ha, photon to thel B2 spectrum, obtained in the scheme of Fig.l,...

A beautiful experiment demonstrating coherent control in the sense of the Tannor-Kosloff-Rice scheme was carried out by Baumert et al. [17] using resonant three-photon ionization and fragmentation of Na2. 

Figure 6.14 Phase lag spectrum (top) for the photodissociation and photoionization of HI fftircles) and for photoionization of a mixture of HI and H2S (triangles). Bottom two panels are vtfte one- and three-photon ionization speclTa of HI. (From Fig. 7, Ref. [221].)...

The general depiction of a one-color, three-photon ionization contains four experimental outcomes. These occur when the energy of the multiple of excitation photons (a) does not match a stationary excited state of the system or (b) matches some stationary resonance RS state of the system or when the ion is produced (c) in an excited, ion state (/ ), or (d) in excited, continuum states which, thereafter, ionize (i.e. ATI). The kinetic energy of the ejected electron in (b) is KE = 3hv - /. In cases (c) and (d), electrons of energy KE2 = 3hv -I and KE3 = 4hv - /, respectively, are observed (Figure 4). 

Figure 9 1S-2S resonant three photon ionization of positronium. 

Figure 11 Resonant three-photon ionization of positronium due to l S,+3/jv->2 Si+/ v->e +e . The Te2 reference tine has been split into three lines by acousto-optically modulating the cw dye laser at 50 MHz. For this scan, the line center was 25.9+2.7 MHz above the Te2 line.

J.F. Kelly, J.P. Hessler, G. Alber, Experimental studies of three-photon ionization of Ba Evidence of channel interference and Raman coupling, Phys. Rev. A 33 (1986) 3913. 

Fig. 14. Temporal evolution of a transient three-photon ionization signal of decaying Na2K (a) and its emerging fragment NaK (b). The decay time of the excited trimcr corresponds well to the rise time of its diatomic fragment. The superposed oscillations indicate wave packet oscillations in the coherently excited system.

Another very sensitive detection scheme is based on resonant two- or three-photon ionization of atoms and molecules in the gas phase (Sect. 1.3). With this technique even liquid or solid samples can be monitored if they can be vaporized in a furnace or on a hot wire. If, for instance, a heated wire or plate in a vacuum system is covered by the sample, the atoms or molecules are evaporated during the pulsed heating period and fly through the superimposed laser beams Li- -L2(-f-L3) in front... 

Another very sensitive detection scheme is based on resonant two- or three-photon ionization of atoms and molecules in the gas phase (Sect. 6.3). With this technique even liquid or solid samples can be monitored if they can be vaporized in a furnace or on a hot wire. If, for instance, a heated wire or plate in a vacuum system is covered by the sample, the atoms or molecules are evaporated during the pulsed heating period and fly through the superimposed laser beams L1+L2 (+L3) in front of the heated surface (Fig. 15.2). The laser LI is tuned to the resonance transition /> - k) of the wanted atom or molecule while L2 further excites the transition k) f). Ions are formed if Ef is above the ionization potential IP. The ions are accelerated toward an ion multiplier. If L2 has sufficient intensity, all excited particles in the level / ) can be ionized and all atoms in the level [/ flying through the laser beam during the laser pulse can be detected single-atom detection) [15.10-15.12]. If... 

In Sect. 3.1.1, for a similar system, the model molecule K2 excited to its A state, the wave packet propagation is explored in greater detail by real-time three-photon ionization (3PI) spectroscopy. Applying laser pulses of moderate intensities allows the selective detection of the pure vibrations of the A state, in excellent agreement with quantum dynamical calculations [42]. Both the favorable spectroscopic properties of K2 and the special molecular dynamics induced by the selected moderate laser intensity combine to open... 

The resulting real-time spectrum of a one-color three-photon ionization (3PI) is shown in Fig. 3.4 over a range of about 200 ps. The excitation wavelength was A = 833.7 nm (12 040.81 cm ). The quadrupole mass spectrometer was aligned to the maximum ion yield of the isotope of the... 

Third, the first maximum is not found at At = 0, but at T

important information about the transition pathway during the induced three-photon ionization process. The pump pulse prepares the wave packet at the inner turning point of the A state. Then the wave... 

Most of the real-time experiments on alkali dimers performed so far have used - as introduced above - three-photon ionization (see also Sects. 3.1.3-3.1.6). However, applying an ultrastable femtosecond laser system combined with a long-time stable molecular beam allows also a straightforward approach by two-photon ionization. In this case the observed wave packet propagation in the A state is not at all superimposed by any influence... 

Fig. 3.20. Potential-energy surfaces of Na2 involved in the three-photon ionization process (taken from [333]). Different transition pathways (a) and (b), found for excitation with Apump = 620 nm...

M. Broyer, J. Chevaleyre, G. Delacretaz, S. Martin, and L. Woste, K2 Rydberg State Analysis by Two- and Three-Photon Ionization , Chem. Phys. Lett. 99, 206 (1983). 

D. Dechamps, L. Roos, C. Delfin, A. L Huillier, C.-G. Wahlstrom Two-and three-photon ionization of rare gases using femtosecond harmonic pulses generated in a gas medium. Phys. Rev. A64, 031404/1-4 (2001)... 

In condensed media, proper determination of the energetics of the photoionization process requires proper identification of the ionization mechanism(s). The latter can become complicated depending on the characteristics of the laser source used and the characteristics of the resonance states involved, especially their lifetimes and intramolecular relaxation pathways. To illustrate this we again refer to Fig. 25 where the arrows designate various photoionization mechanisms for a molecule embedded in a (nonpolar) liquid. (Note that we use the same energy levels as in the low-pressure gas although the position of these levels should be lowered in the liquid.) These include (i) direct nonresonant one-photon (process 1), two-photon (process 3), and three-photon (process 6) ionization (ii) direct one-photon (process 2), two-photon (process 4), and three-photon (process 7) ionization resonant with a superexcited state (iii) three-photon ionization which is two-photon resonant with an excited state below 1. Concerning the last case (case iii), Faidas and Christophorou (1987, 1988) found that for aromatic molecules in nonpolar... 

The results of a laser multiphoton ionization (MPI) study of fluoranthene in tetramethylsilane (TMS) and of azulene in n-tridecane (TRD), n-pentane (PNT), 2,2,4,4-tetramethylpentane (TMP), TMS and tetramethyltin (TMT) are reported. Three types of MPI mechanisms have been identified in all solute/solvent systems 1) two-photon ionization occurring at laser wavelengths X < 400-480 nm depending on the solute and the solvent 2) stepwise three-photon ionization occurring for X>... 

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