# Finding the number density of atomic vapor by studying its absorption profile

## TL;DR

This paper presents a spectroscopic method to determine atomic vapor density by fitting absorption spectra with a density-matrix model, applied to cesium vapor at room temperature, accounting for line asymmetry and evaporation heat.

## Contribution

The paper introduces a novel technique combining absorption spectrum fitting with a density-matrix model to accurately measure atomic vapor density and evaporation heat.

## Key findings

- Successful application to cesium vapor at room temperature
- Accurate modeling of spectral asymmetry due to open transitions
- Determination of latent heat of evaporation from density-temperature data

## Abstract

We demonstrate a technique for obtaining the density of atomic vapor, by doing a fit of the resonant absorption spectrum to a density-matrix model. In order to demonstrate the usefulness of the technique, we apply it to absorption in the ${\rm D_2}$ line of a Cs vapor cell at room temperature. The lineshape of the spectrum is asymmetric due to the role of open transitions. This asymmetry is explained in the model using transit-time relaxation as the atoms traverse the laser beam. We also obtain the latent heat of evaporation by studying the number density as a function of temperature close to room temperature.