These Laser-Induced Fluorescence (LIF) system contain a photomultiplier tube (PMT) and base, cut-off filter compartment, and vacuum sealed iodine cell. The wavelength of a tunable commercial laser, such as, a continuous wave (cw) diode or pulsed dye laser, are often off be some small amount and typically do not scan linear in energy. A common practice is to simultaneously record a reference spectrum of an atom or molecule with well-known transitions energies. This allows the collected spectral data to be accurately calibrated.
This system allows for the collection of the LIF spectrum of iodine which can be used as a reference spectrum. The absorption spectrum of iodine (often recorded with cw lasers) is typically accomplished by placing a photodiode at the output side of the reference cell. The LIF technique is more applicable to pulsed lasers with high peak power, such as, dye and optical parametric oscillator (OPO) laser systems.
The iodine cell is made from a flame-sealed quartz cell and is mounted inside a heavy duty conflat cross making it nearly unbreakable. An integrated fluorescence collection optic is mounted in a sliding mount to allow great light gathering capability, so that the iodine fluorescence is imaged onto the photocathode of the photomultiplier tube. This LIF system allows for excellent signal-to-noise spectra to be collected from low power pulsed laser systems.
These systems can be ordered with or without a built-in iodine cell heating system. The heated version includes integrated cartridge heaters, thermocouple, and proportional-integral-derivative (PID) controller/power supply so that the operator can select a desired set point temperature anywhere from room to 250 °C. The room temperature and or heated B-X spectrum of Iodine contains thousands for rovibrational transitions that are well known being a continuous spectrum from 14,800 to 20,000 cm-1.
The figure below shows a sample LIF spectrum of iodine recorded with a pulsed dye laser which has a 0.04 cm-1 linewidth. The spectrum was collected using a 0.003 cm-1 step size, 10 laser shot averages, and calibrated with 24 iodine lines to an rms of 0.002 cm-1. In these experiments, the PMT tube is supplied -850 VDC for a high voltage power supply, a 645 nm long wavelength pass cutoff filter was used to block the laser’s scattered light, the LIF analog signal was captured with a gated integrator, and recorded with our data acquisition system. The LIF spectrum of iodine is easy to power broaden, we recommend installing a diverging lens and using neutral density filters before the input optical arm to lower the amount of laser energy going through the LIF system. A good rule of thumb is to lower the lasers power until it is only barely visible as seen on a white business card with the room lights out. This is a good starting point to ensure that the iodine lines are as sharp as possible without power broadening effects.
This laser-induced fluorescence system includes optical arms to limit background noise from the room’s lights and to well define the optical axis which makes laser alignment easier. These LIF systems are support by 3 optical table ½” posts (including post holders and 1” pedestals) for easy mounting and leveling onto any optical table. We also offer many accessories, such as, 2 inch square long wavelength pass optical cutoff filters so that scattered laser light is blocked from view by the PMT, adjustable high-voltage power supply for the PMT, gated integrators, printed copies of the I2 atlas, and data acquisition software.
This system pricing includes a red sensitive Hamamatsu R955 photomultiplier tube and base (wide spectral response 160 to 900 nm).
