![]() ![]() Numerical simulations were done using the atomic density-matrix (ADM) package for Mathematica developed by Simon Rochester (can be downloadedfrom ). The relevant en-ergy levels are shown in Fig. As an example ofthe power of this technique, we consider hyperfine transitions inĬs. On the otherhand, open transitions can decay to a different ground level this necessitates the use of atwo-region model-one region where the laser beam is present and one where it is not-something which can be easily incorporated into any numerical package. Closed transitions-thosethat decay back to the same ground level-behave like two-level systems. However, transitions in a real atom involve multiple hyperfine levels, whichnecessitates the use of a numerical density-matrix approach. The absorption of an ideal two-level system is a standard problem discussed in manytextbooks. The data is acquired on a computer through a RS232 serialcommunication link. The controller also acquiresdata from the CoSy system, which provides a saturated-absorption signal, both with andwithout a Doppler background. Optical feedback to reduce the linewidth of the laser isrovided by a piezo-mounted grating, and the piezo voltage is also set by the controller.The laser frequency is scanned by varying the piezo voltage. The laser controller controls the injection current intothe diode and its temperature. The fiber goes into a 95/5 power splitter, with 5% of the power fed to a TopticaįIG. The laser output comes out of a single-mode polarization-maintaining (PM)fiber. The laser beam is derivedfrom a commercial diode laser system (Toptica DL Pro) operating near the 852 nm D line of Cs. The experimental set up is shown schematically in Fig. We also obtain the latent heat ofevaporation by studying the number density as a function of temperature. ![]() While number density alone is enough to explainthe height of the absorption curve, its asymmetric lineshape requires the use of transit-time relaxation as the atoms traverse the laser beam. The basic idea is to use the percentage absorption through a vapor cell.As an example, we demonstrate the usefulness of the technique by measuring the numberdensity of Cs atoms at room temperature. In addition, simplifying assumptions such as the vapor behaving as anideal gas have to be made in order to relate the vapor pressure to a number density.In this work, we present an experimental technique to make an accurate estimate of thenumber density. While vapor pressure curves areavailable for most atoms, they are not sufficiently accurate to allow them to be used insuch calculations. INTRODUCTION Theoretical calculations of atomic transition linewidths and strengths requireprecise knowledge of the number density of the vapor. We alsoobtain the latent heat of evaporation by studying the number density as a function of temperatureclose to room temperature.Keywords: Number density Absorption curve Density-matrix analysis. This asymmetry isexplained in the model using transit-time relaxation as the atoms traverse the laser beam. In order to demonstrate the usefulnessof the technique, we apply it to absorption in the D line of a Cs vapor cell at room temperature.The lineshape of the spectrum is asymmetric due to the role of open transitions. ![]() We demonstrate a technique for obtaining the density of atomic vapor, by doing a fit of theresonant absorption spectrum to a density-matrix model. Harish Ravi, Mangesh Bhattarai, and Vasant Natarajan ∗ Department of Physics, Indian Institute of Science, Bangalore-560012, India J un Finding the number density of atomic vapor by studying itsabsorption profile ![]()
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