Obtaining two attosecond pulses for X-ray stimulated Raman spectroscopy

Attosecond X-ray pulses are an indispensable tool for the study of electronic and structural changes in molecules undergoing chemical reactions. They have a wide bandwidth comparable to the energy bands of valence electronic states and, therefore, are well suited for making and probing multiple valence electronic excitations using core electron transitions. Here we propose a method of creating a sequence of two attosecond soft X-ray pulses in a free electron laser by optical manipulation of electrons located in two different sections of the electron bunch. The energy of each X-ray pulse can be of the order of 100 nJ and the pulse width of the order of 250 as. The carrier frequency of each X-ray pulse can be independently tuned to a resonant core electron transition of a specific atom of the molecule. The time interval between the two attosecond pulses is tunable from a few femtoseconds to a hundred femtoseconds with better than 100 as precision. (C) 2009 Elsevier B.V. All rights reserved.