TY - JOUR

T1 - Analytical model of transit time broadening for two-photon excitation in a three-level ladder and its experimental validation

AU - Bruvelis, M.

AU - Ulmanis, J.

AU - Bezuglov, N.N.

AU - Miculis, K.

AU - Andreeva, C.

AU - Mahrov, B.

AU - Tretyakov, D.

AU - Ekers, A.

PY - 2012

Y1 - 2012

N2 - We revisit transit time broadening for one of the typical experiment designs in molecular spectroscopy, that of a collimated supersonic beam of particles crossing a focused Gaussian laser beam. In particular, we consider a Doppler-free arrangement of a collimated supersonic beam of Na2 molecules crossing two counterpropagating laser beams that excite a two-photon transition in a three-level ladder scheme. We propose an analytical two-level model with a virtual intermediate level to show that the excitation line shape is described by a Voigt profile and provide the validity range of this model with respect to significant experimental parameters. The model also shows that line broadening due to the curvature of laser field wave fronts on the particle beam path is exactly compensated by increased transit time of particles farther away from the beam axis, such that the broadening is determined solely by the size of the laser beam waist. The analytical model is validated by comparing it with numerical simulations

AB - We revisit transit time broadening for one of the typical experiment designs in molecular spectroscopy, that of a collimated supersonic beam of particles crossing a focused Gaussian laser beam. In particular, we consider a Doppler-free arrangement of a collimated supersonic beam of Na2 molecules crossing two counterpropagating laser beams that excite a two-photon transition in a three-level ladder scheme. We propose an analytical two-level model with a virtual intermediate level to show that the excitation line shape is described by a Voigt profile and provide the validity range of this model with respect to significant experimental parameters. The model also shows that line broadening due to the curvature of laser field wave fronts on the particle beam path is exactly compensated by increased transit time of particles farther away from the beam axis, such that the broadening is determined solely by the size of the laser beam waist. The analytical model is validated by comparing it with numerical simulations

KW - three-level ladder scheme

KW - Gaussian laser beams

KW - excitation fluorescence

KW - transit time broadening

U2 - 10.1103/PhysRevA.86.012501

DO - 10.1103/PhysRevA.86.012501

M3 - Article

VL - 86

SP - 012501_1-9

JO - Physical Review A - Atomic, Molecular, and Optical Physics

JF - Physical Review A - Atomic, Molecular, and Optical Physics

SN - 1050-2947

IS - 1

ER -