Photon echo

Figure Al.6.24. Schematic representation of a photon echo in an isolated, multilevel molecule, (a) The initial pulse prepares a superposition of ground- and excited-state amplitude, (b) The subsequent motion on the ground and excited electronic states. The ground-state amplitude is shown as stationary (which in general it will not be for strong pulses), while the excited-state amplitude is non-stationary. (c) The second pulse exchanges ground- and excited-state amplitude, (d) Subsequent evolution of the wavepackets on the ground and excited electronic states. Wlien they overlap, an echo occurs (after [40]).

Although the early photon echo experiments were cast in tenns of Ji/2 and n pulses, these precise inversions of the population are by no means necessary [Ml- hr fact echoes can be observed using sequences of weak... 

Tannor D J and Rice S A 1987 Photon echoes in multilevel systems Understanding Molecular Properties ed J Avery et al (Dordrecht Reidel) p 205... 

Shen Y R 1984 The Principles of Nonlinear Optics (New York Wiley) ch 21 for a clear discussion of the connection between the perturbative and nonperturbative treatment of photon echoes... 

Asaka S, Nakatsuka H, Fujiwara M and Matsuoka M 1984 Accumulated photon echoes with incoherent light in Nd -doped silicate glass Rhys. Rev. A 29 2286-9... 

Beech R and Hartmann S R 1984 Incoherent photon echoes Rhys. Rev. Lett. 53 663-6... 

Figure B2.1.10 Stimulated photon-echo peak-shift (3PEPS) signals. Top pulse sequence and iuterpulse delays t and T. Bottom echo signals scaimed as a fiinction of delay t at tluee different population periods T, obtained with samples of a tetrapyrrole-containing light-harvesting protein subunit, the a subunit of C-phycocyanin.

Becker P C, Fragnito H L, Bigot J-Y, Brito Cruz C H, Fork R L and Shank C V 1989 Femtosecond photon echoes from molecules in solution Phys. Rev. Lett. 63 505-7... 

Bigot J-Y, Portella M T, Schoenlein R W, Bardeen C J, Migus A and Shank C V 1991 Non-Markovian dephasing of molecules in solution measured with three-pulse femtosecond photon echoes Phys. Rev. Lett. 66 1138 1... 

Passino S A, Nagasawa Y, Joo T and Fleming G R 1996 Photon echo measurements in liquids using pulses longer than the electronic dephasing time Ultrafast Phenomena X ed P Barbara, W Knox, WZinth and J Fujimoto (Berlin Springer) pp 199-200... 

Homoelle B J, Edington M D, Diffey W M and Beck W F 1998 Stimulated photon-echo and transientgrating studies of protein-matrix solvation dynamics and interexciton-state radiationless decay in a phycocyanin and allophycocyanin J. Phys. Chem. B 102 3044-52... 

Pshenichnikov M S, Duppen K and Wiersma D A 1995 Time-resolved femtosecond photon echo probes bimodal solvent dynamics Phys. Rev. Lett. 74 674-7... 

Tokmakoff A, Zimdars D, Urdahl R S, Francis R S, Kwok A S and Fayer M D 1995 Infrared vibrational photon echo experiments in liquids and glasses J. Phys. Chem. 99 13 310-20... 

Tokmakoff A and Fayer M D 1995 Homogeneous vibrational dynamics and inhomogeneous broadening in glass-forming liquids infrared photon echo experiments from room temperature to 10 KJ. Chem. Phys. 103 2810-26... 

Tokmakoff A and Fayer M D 1995 Infrared photon echo experiments exploring vibrational dynamics in liquids and glasses Acc. Chem. Res. 28 439—45... 

Zilker S J, Kador L, Friebel J, Vainer Y G, Kol chenko M A and Personov R I 1998 Comparison of photon echo, hole burning, and single molecule spectroscopy data on low-temperature dynamics of organic amorphous solids J. Phys. Chem 109 6780-90... 

Hesselink W H and Wiersma D A 1983 Theory and experimental aspects of photon echoes in molecular solids... 

Cho, M. and Fleming, G. R. Photon-echo measurements in liquids numerical calculations with model systems, J. Chem.Phys 98 (1993), 2848-2859... 

Shortly thereafter came reports of integrated three-pulse photon echoes, especially using the echo peak shift to provide information about spectral diffusion [21, 23]. In one experiment [10, 23] the peak shift shows an intriguing oscillation at short times with a period of about 180 fs, followed by a slower relaxation with a decay time of 1.4 ps. The three-pulse echo amplitude can also be heterodyned, leading to 2DIR experiments [24 26]. The latter experiments provide a wealth of information, and there are several ways to extract the desired spectral diffusion dynamics [149]. 

Photon echo and IR pump-probe experiments can also be performed on neat water, but one needs a very small sample. Fabrication of nano-fluidic Si3Ni4 sample cells have opened up this new and exciting field, and data from these experiments, performed by the Elsaesser and Miller groups, have recently been reported [73, 74]. At room temperature, spectral evolution occurs within 50 fs, and polarization anisotropy decays within 75 fs. At temperatures just about the freezing point, spectral evolution slows down dramatically [74],... 

The reduction of obtainable light-pulse durations down to subpicosecond pulses (halfwidth about 10 sec) allows fast transient phenomena which were not accessible before to be studied in the interaction of light with matter. One example is the extension of spin echoe-techniques, well known in nuclear-magnetic-resonance spectroscopy, to the photon echoes in the optical region. 

Femtosecond photon echo measurements of electronic coherence relaxation of I2 in the presence of He, Ar, N2,02, C3H8... 

Photon Echo (PE) and Reverse Transient Grating (RTG) measurements of the loss of electronic coherence between the X( 2g+) and B(3FIou+) states of molecular iodine are measured by three pulse four wave mixing (FWM). Two cases are considered, relatively low pressure isolated iodine (1-2 Torr), and iodine at high pressure (>10torr) or in the presence of several hundred Torr of buffer gas. 

Spectrally resolved femtosecond two-colour three-pulse photon echoes for studies of molecular dynamics influence of pulse wavelengths and pulse sequence... 

In this paper we report the use of spectrally resolved two-colour three-pulse photon echoes to expand the information that can be obtained from time-resolved vibrational spectroscopy. The experiments allow the study of intramolecular dynamics and vibrational structure in both the ground and excited electronic states and demonstrate the potential of the technique for studying structural dynamics. 

In a two-colour three-pulse photon echo experiment we illuminate the sample with two pump pulses delayed by time ti2 and having wave vectors ki and k2 at the same wavelength followed by a probe pulse of wave vector kj delayed with respect to the second pump pulse... 

Fig. 2. Photon echo spectra vs. population time (a, d) and coherence time (b, c, e, 1) at fixed other delay time for pump or probe pulse wavelength at the maximum (575 nm) and on the blue side (560 nm) of the absorption maximum. The inset shows the contour plot of corresponding figure...

In summary, spectrally resolved 3-pulse 2-colour photon echoes provide a potential tool to study the molecular structure dynamics on a femtosecond time scale and will be used to study chemical and physical processes involving nonequilibrium relaxation in both ground and excited states of molecules. 

---