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Summary form only given. The ground electronic state is where most chemical reactions take place, and therefore, the ability to prepare molecules in highly excited, nonthermal states is an excellent starting point for controlling chemical reactions. In order to prepare a molecule in a significantly non-thermal way, the preparation must be completed on a time scale short compared to the energy redistribution time, of the order of a picosecond. Moreover, the Franck-Condon factor dictates very low probability to directly excite a high vibrational state when starting from a molecule in its lowest states, due to minimal wavefunction overlaps between the states. Further experimental complications occur because electronic ground states of molecules do not normally fluoresce or ionize, so that their direct detection is very difficult. We present a method for preparing molecules in arbitrarily high vibrational excited states in the electronic ground states, and provide a built in diagnostics method for detecting these states. In this method, termed (TD)CARS for Two-Dimensional Time-Delayed CARS we prepare a wavepacket in the electronic excited state by means of a short pump pulse. This wavepacket is allowed to propagate in the excited state, and a second, delayed pulse brings it down to the desired ground state wavepacket. The center frequency and delay of the second pulse are optimized by a procedure, which was developed and is discussed. The generated ground state wavepacket is monitored by completing a CARS sequence, thus providing a direct signal from the oscillating high vibrational wavepacket.

Summary form only given. A method based on two separate time delays is demonstrated for the selective femtosecond excitation and observation of different vibrations in the electronic ground state of molecules. The first pulse creates the initial wavepacket in the excited electronic state. Normally, the second (Stokes) pulse would induce transitions back to the ground state, populating the states favorably coupled by a good overlap with the initial wavepacket. Instead, we introduce a variable evolution delay between the first two pulses, thus allowing better overlap of the wavepacket with selected vibrational levels in the ground state. Matching the Stokes frequency is also crucial for efficient population transfer.

Elastic and inelastic neutron scattering studies of the Kondo lattice CeCu2Ge2 were performed. AtTN=4.1 K an incommensurate magnetic order develops with an ordering wave vectorq0=(0.28, 0.28, 0.54) and an ordered moment µs=0.74 µB. The crystalline electric field splits the 4f1-J-multiplet of the Ce ion into a ground state doublet and a quartet at 191 K. The wave function of the ground state yields an ordered moment of 1.54µB. Thus, due to the onset of the formation of a Kondo singlet the magnetic moment is considerably reduced. The magnetic relaxation rate Λ was investigated via quasielastic neutron scattering. The temperature dependence of Λ(T) is characteristic of heavy-fermion systems with a high temperature square root dependence and a limiting low temperature value, yielding a Kondo temperatureTK≈10K. The quasielastic component of the scattered neutron intensities persists down to the lowest temperatures, well belowTN. This quasielastic line is regarded as a characteristic feature of heavy-fermion systems and corresponds to the enhanced value of the linear term of the specific heat.

An inelastic neutron scattering study is performed on the new magnetically ordered heavy-fermion systems CeCu2Ge2 and CeAg2Ge2. The temperature dependence of the quasielastic line can be interpreted in terms of a Kondo type of behavior. In addition crystalline electric field transition energies are reported.

The magnetic relaxation rates Γ as determined via inelastic neutron scattering experiments are reported for the ternary compounds CeM 2 X 2 (M  Ni, Cu, Ag, Au, Ru; X  Si, Ge). Strongly enhanced values of Γ and deviations from a Korringa-type of behaviour were found. A close correlation between the unit cell volume and the 4f-local spin / conduction electron hybridization is demonstrated.

The spin relaxation rates Γ in magnetically ordered Kondo lattices have been determined using neutron scattering techniques. Enhanced values of Γ and distinct deviations from a Korringa-type of relaxation behaviour were found. Gaussian contributions to the quasielastic scattered intensities were interpreted as being due to magnetic fluctuations.