Abstract

An accurate technique has been developed to calculate the equivalent width of absorption lines. The calculations have been carried out for the pure Doppler and pure Lorentz limiting forms of the equivalent width. A novel expression for the equivalent width for Lorentz profile is given from direct integration of the line profile. The more general case of a Voigt profile leads to an analytical formula that permits a rapid estimate of the equivalent width for a wide range of maximum optical depths. The reliability of the approach is verified using a numerical application calculating the equivalent width for nickel resonance lines at 232.0 and 352.3 nm from atomic absorption (AA) measurements. The dependence of equivalent width on the number density of absorbing atoms is also provided. The results obtained for the equivalent width for the Voigt profile were compared with the data in the available literature obtained by different approaches.

Calculations of line absorption for the Voigt profile*

Isamu Kato, Akira Iwasaki, Akihiro Adachi, and Tsukasa Shimizu
J. Opt. Soc. Am. 68(7) 1008-1009 (1978)

Transmission Function for Bands with Doppler-Lorentz Line Shapes

R. F. Hughes, H. Hurwitz, and G. M. Roe
J. Opt. Soc. Am. 50(3) 232-236 (1960)

Collisional narrowing: its effect on the equivalent widths of spectral lines

C. D. Rodgers
Appl. Opt. 15(3) 714-716 (1976)

Calculations of line absorption of specific helium lines for the Voigt profile

Isamu Kato and Akifumi Yonehara
J. Opt. Soc. Am. 72(3) 395-395 (1982)

Simple atmospheric transmittance calculation based on a Fourier-transformed Voigt profile

Hirokazu Kobayashi
Appl. Opt. 41(33) 6937-6940 (2002)