Highly selective pumping of an excited state by Doppler-free multiphoton absorption

A. M. Akulshin, V. L. Velichanskiǐ, R. Gamidov +3 more

Y. B. Band

We study the dynamics of multiphoton-absorption chirped adiabatic passage (CHIRAP) in atoms, and show that the dynamics of the excited-state fine-structure transitions can be nonadiabatic even though the optical transfer to the highly excited electronic states is fully adiabatic. Hence, care must be taken to ensure that the dynamics is selective if multiphoton-absorption CHIRAP is to be used as a pump- ing mechanism to populate very-high-lying states that can serve as the pumping levels for uv lasers. We investigate the dynamics as a function of chirp rate and field intensity in the 5s $^{2}$${\mathit{S}}_{1/2}$\ensuremath{\rightarrow}5p $^{2}$${\mathit{P}}_{3/2}$\ensuremath{\rightarrow}5d $^{2}$${\mathit{D}}_{3/2}$,5d $^{2}$${\mathit{D}}_{5/2}$ rubidium system, and show that selectivity can be maintained despite the near degeneracy of the $^{2}$D manifold.

E. Giacobino, Elizabeth Giacobino

Anne L’Huillier, Louis A. Lompre, G. Mainfray +1 more

This paper describes the production of multiply charged ions induced by collisionless multiphoton ionization of rare gases at 532 and 1064 nm. The production of multiply charged ions emphasizes atomic properties and laser characteristics. Multiphoton absorption is expected to selectively excite high ionic energy states, which could induce a stimulated emission in the extreme ultraviolet.

Pedro F. González-Dı́az

W. S. Warren, Ahmed H. Zewail

In this paper we present novel and simple pulse sequences for enhancing the intensity of forbidden or highly nonresonant optical transitions. These sequences provide a straightforward approach to circumventing the most serious limitation of optical coherent transient spectroscopy: Available laser intensities are often insufficient to excite a significant fraction of the ground state population into desired excited states, either because of large inhomogeneous broadening or, in the case of multiphoton absorption, large anharmonicities. Optical phase modulation (which can be produced by an acousto-optic modulator) or amplitude modulation (which can be produced by an interferometer) with carefully chosen pulse flip angles and delays can effectively remove even very large energy mismatches, thus permitting essentially complete population inversions arbitrarily far from resonance. Coherent averaging theory and computer calculations are used to derive particularly valuable sequences. Pumping enhancement of 103–105 (depending on individual molecular parameters) for these modulated pulse sequences are predicted. Specific applications to multiphoton pumping of local vibrational modes are discussed.