Question

Concentrations (pg per g of snow) of metals by atomic fluorescence in the Agassiz Ice Cap in Greenland for the period1988 - 1992are${}^{\mathbf{38}}\mathit{P}\mathit{b}\mathbf{,}\mathbf{1}\mathbf{.}{\mathbf{0}}_{\mathbf{4}}\left(\pm 0.1_7\right)\mathbf{\times }{\mathbf{10}}^{\mathbf{2}}\mathbf{;}\mathit{T}\mathit{I}\mathbf{,}\mathbf{0}\mathbf{.}\mathbf{43}\mathbf{\pm }\mathbf{0}\mathbf{.}{\mathbf{08}}_{\mathbf{7}}\mathbf{;}\mathit{C}\mathit{d}\mathbf{,}\mathbf{3}\mathbf{.}\mathbf{5}\mathbf{\pm }\mathbf{0}\mathbf{.}{\mathbf{8}}_{\mathbf{7}}\mathbf{;}\mathit{Z}\mathit{n}\mathbf{,}\mathbf{1}\mathbf{.}{\mathbf{7}}_{\mathbf{4}}\left(\pm 0.2_6\right)\mathbf{\times }{\mathbf{10}}^{\mathbf{2}}\mathbf{;}$ and $\mathit{A}\mathit{I}\mathbf{.}{\mathbf{6}}_{\mathbf{-}\mathbf{1}}\left(\pm 1_{-7}\right)\mathbf{\times }{\mathbf{10}}^{\mathbf{3}}$ . The mean annual snowfall was $\mathbf{11}\mathbf{.}\mathbf{5}\mathit{g}\mathbf{/}\mathit{c}{\mathit{m}}^{\mathbf{2}}$ . Calculate the mean annual flux of each metal in units of $\mathit{n}\mathit{g}\mathbf{/}\mathit{c}{\mathit{m}}^{\mathbf{2}}$ . Flux means how much metal falls on each $\mathit{c}{\mathit{m}}^{\mathbf{2}}$ .

Short answer

A wide envelope is visible because the monochromator's bandwidth is insufficient to differentiate between wavelengths.

Step-by-step solution

Define linewidth and bandwidth.

While there are stricter definitions for each term, bandwidth typically refers to the range of frequencies or wavelengths that a laser can produce, whilst linewidth typically refers to the full-width at half-maximum of the emitted light in the optical spectrum.

The excitation linewidths be much narrower than the detector monochromator bandwidth.

The laser atomic fluorescence excitation spectra of sodium produce two sharp lines in an air-acetylene flame, whereas the emission spectrum produces a single broad band. While the sample is activated with several narrow bands , the excitation spectrum looks at emission across a $\left(0.03nm\right)$ band. Only when the laser and atomic frequencies match does the sample absorb light. When the narrow laser line resonates with the atomic levels, emission occurs.

A laser stimulates the sample in the emission spectrum, which then emits radiation. A wide envelope is visible because the monochromator's bandwidth is insufficient to differentiate between wavelengths.