Double-quantum spectroscopy of dense atomic vapors: Interplay between Doppler and self-broadenings

In this article, we present a simulation study of the linear and nonlinear spectroscopy of dense atomic vapors. Motivated by recent experiments, we focus on double quantum spectroscopy, which directly probes dipole-dipole interactions. By explicitly including thermal velocity, we show that temperature has an important impact on the self-broadening mechanisms of the linear and nonlinear spectra. We also provide analytical expressions for the response functions in the short time limit using the two-body approximation, which shows that double quantum spectroscopy for atomic vapors directly probes the transition amplitude of the electronic excitation between two atoms. We also propose an expression for the double quantum spectrum that includes the effect of Doppler broadening, and we discuss the effect of density on the spectrum. We show that when Doppler broadening is negligible compared to self-broadening, the double quantum spectrum scales with the atomic density, while when Doppler broadening dominates, it scales as the square of the density.

Automated summary

In this article, the simulation study of the linear and nonlinear spectroscopy of dense atomic vapors is presented. It is shown that temperature has an important impact on the self-broadening mechanisms of the linear and nonlinear spectra by including thermal velocity explicitly. The response functions in the short time limit are provided using the two-body approximation, revealing that double quantum spectroscopy directly probes the transition amplitude of the electronic excitation between two atoms in atomic vapors. An expression for the double quantum spectrum that includes the effect of Doppler broadening is proposed, and the effect of density on the spectrum is discussed. It is demonstrated that the double quantum spectrum scales with the atomic density when Doppler broadening is negligible compared to self-broadening, while it scales as the square of the density when Doppler broadening dominates.