Quantum Control of Wave Packet Evolution with Tailored Femtosecond Pulses

Abstract

Using theory to guide the choice of pulse shape, we have synthesized frequency-chirped laser pulses and used them to control the evolution of vibrational wave packets on the 8 excited state of iodine.A negatively chirped pulse produces a wave packet at the The spread of the target in position and momentum is given by the formulas Ax = Qh/2m' and Ap = /mesh/2, where m is the reduced mass of the iodine molecule and the parameter co (units of frequency) was chosen to correspond to 250 cm '. The target is centered about a chosen position (0.372 nm) and a chosen momentum (corresponding to a kinetic energy of 50 meV).In this case, the momentum is negative, meaning that the iodine atoms are moving toward each other. The target is achieved by using a tailored, ultrashort light field to create an initial wave packet that evolves under the influ- state at a later time. The wave packet evolution is monitored by exciting the wave packet to the higher-lying e state with a second ultrashort pulse which opens up a "window" in internuclear distance (shown schematically by the striped box).The experimental signal is the total laser-induced fluorescence (LIF) from the e state as a function of delay between the pump and probe pulses, allowing detection of the wave packet density in a region of internuclear distance selected by the probe wavelength.ence of the molecular Hamiltonian to yield a wave packet that has maximum overlap with the target distribution at a later time. To reach the target in a reasonable amount of time, the electric field is allowed to be nonzero only during a temporal interval of our choice (550 fs, in the present case). Thus, the task of theory is to find the electric field F(t) that best steers the system to our chosen target at the chosen time. We note that to achieve this target, the optimal field must overcome the wave packet spreading which ordinarily occurs in anharmonic potentials. 33600031-9007/95/74(17)/3360(4)$06. 00

Intrapulse Dynamical Effects in Multiphoton Processes: Theoretical Analysis

“…Even in the weak response limit, the sign of the chirp proves crucial in wave packet focusing and defocusing, even though the total population being excited is a function only of the power spectrum. 7 In a pumpdump or pump-probe experiment, the chirp of the second pulse can be optimized to follow the motion of the wave packet induced by the pump pulse, hence improving the quantum yield substantially. 8,9 This chirp following effect becomes an intrinsic feature of multiphoton and strong-field optical processes.…”

A single isolated sub-50 attosecond pulse generation with a two-color laser field by a frequency-chirping technique

“…Frequency-chirping, i.e., a time-dependent change in the laser frequency during the pulse provides a new and easy way to create and control a focused wavepacket of the laser field [16][17][18]. It is usually easier to induce a chirping into a femtosecond pulse than to obtain a specific pulse shape.…”

Adiabatic Passage in a Three-State System with Non-Markovian Relaxation: The Role of Excited-State Absorption and Two-Exciton Processes

“…The possibility of the optical control of molecular dynamics using properly tailored pulses has been the subject of intensive studies in the last few years [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. Chirped pulses can selectively excite coherent wave packet motion either on the ground electronic potential energy surface of a molecule or on the excited electronic potential energy surface due to the intrapulse pump-dump process [1,5,11,12].…”