A Doppler background that is due to velocity-changing collisions, which may severely limit the resolution, can be greatly reduced by the choice of buffer gas. Spectra with sub-Doppler resolution of Ca i transitions at 423 (resonant), 610, 612, 616, 645, 657 (intercombination), and 672 nm were obtained by optogalvanic saturation spectroscopy in lamps filled with argon (0.6 and 2.5 Torr) and krypton (0.6 Torr). We investigated the use of hollow-cathode discharges for high-resolution and high-sensitivity spectroscopy, using atomic calcium. Note: Author names will be searched in the keywords field, also, but that may find papers where the person is mentioned, rather than papers they authored.Use a comma to separate multiple people: J Smith, RL Jones, Macarthur.Use these formats for best results: Smith or J Smith.For best results, use the separate Authors field to search for author names.Use quotation marks " " around specific phrases where you want the entire phrase only.Question mark (?) - Example: "gr?y" retrieves documents containing "grey" or "gray".Asterisk ( * ) - Example: "elect*" retrieves documents containing "electron," "electronic," and "electricity".Improve efficiency in your search by using wildcards.
Example: (photons AND downconversion) - pump.Example: (diode OR solid-state) AND laser.Note the Boolean sign must be in upper-case. Separate search groups with parentheses and Booleans.Keep it simple - don't use too many different parameters.The power supply current range is 0 to 25mA and a 600V ignition followed with 300V sustained power. This is often aided by use of a lock-in circuit. By looking for a resonance on a data plot of the voltage signal versus source tuning parameter, the light source can be tuned to the desired frequency. To tune the light source to a specific transition frequency, a tuning parameter (often the driving current) of the light source is varied. The newly created ions cause an increase in the current across the cathode/anode and a resulting change in the voltage, which can then be measured.
Indirect photoionization can then occur when electron collisions with the excited atom eject an atomic electron. By shining the light source into the HCL, one can excite or even eject electrons (directly photoionize) from the atoms inside the lamp, so long as the light source includes frequencies corresponding to the right atomic transitions. Īn HCL can also be used to tune light sources to a specific atomic transition by making use of the optogalvanic effect, which is a result of direct or indirect photoionization. These photons will then excite the atoms in the sample, which will release their own photons and be used to generate data. As these excited atoms decay to lower states, they will emit photons. Both the buffer gas and the sputtered cathode atoms will in turn be excited by collisions with other atoms/particles in the plasma. The buffer gas ions will then be accelerated into the cathode, sputtering off atoms from the cathode. A large voltage across the anode and cathode will cause the buffer gas to ionize, creating a plasma. Īn HCL usually consists of a glass tube containing a cathode, an anode, and a buffer gas (usually a noble gas). An HCL takes advantage of the hollow cathode effect, which causes conduction at a lower voltage and with more current than a cold cathode lamp that does not have a hollow cathode. for atomic absorption spectrometers) and as a frequency tuner for light sources such as lasers.
0 kommentar(er)
