FAQ: Will my samples be damaged during measurements?

FAQ series: This series of publications explores some of the most often-asked questions regarding Timegated^® spectrometers and measurements without having you read page after page of text.

Many of our customers work with complex materials that should not be damaged during measurements. Therefore, a common question when considering analytical techniques is whether the process itself might alter or damage the sample being studied. While Raman spectroscopy is often described as a non-destructive technique, it's essential to understand the nuances and how advanced methods like Timegated® Raman spectroscopy offer enhanced protection for your valuable samples.

Factors Causing Potential Damage and Alteration to the Sample During Raman Measurements

Under certain conditions, sample damage or degradation can occur during conventional Raman spectroscopy. The primary factor contributing to this potential damage is the laser excitation source used to probe the sample.

High laser power density, particularly when the laser is tightly focused through a microscope objective, can potentially lead to sample degradation. Similarly, using high laser peak power, especially at low repetition rates, has been observed to cause damage to the sample surface. The choice of laser wavelength also plays a role; using lasers in certain ranges, such as the UV spectral range, can increase the risk of sample degradation.

Minimizing the Risk of Sample Damage with Timegated® Raman Spectroscopy

Timegated® Raman spectroscopy is specifically designed to tackle the "Achilles' heel" of conventional Raman spectroscopy: sample-induced fluorescence emission. Fluorescence can easily mask the weaker Raman signal, making it difficult to obtain a usable spectrum with lower laser power. With efficient fluorescence suppression, the Timegated® PicoRaman M3 instrument enables adjustments to laser power, allowing for reductions to smaller power levels for sensitive samples without compromising on Raman signal, unlike many other spectroscopy methods.

Timegated® Technology addresses this in several ways:

• Real Fluorescence Suppression: The core principle is to separate the very short-lived Raman signal from the typically longer-lived fluorescence in the temporal domain. Using a pulsed laser and a precisely synchronised detector, the system is "gated" to collect signals only during the brief moment the Raman photons arrive, while rejecting the fluorescence photons that arrive later.
• Reduced Need for Excessive Laser Power: By effectively suppressing fluorescence interference and other background disturbances, time-gated Raman allows for improved signal detection and a better signal-to-noise ratio (SNR). This means you can often achieve sufficient signal intensity by using moderate laser power levels, rather than needing to increase power to overcome a strong fluorescence background, which directly reduces the risk of laser-induced sample damage.
• Non-Destructive Insights: Timegated® Technology provides quick and non-destructive insights into molecular compositions. The ability to achieve high-quality spectra from fluorescent samples without the need for high laser power or extended acquisition times makes it an ideal method for delicate or sensitive materials.

While high laser peak power at low repetition rates can cause sample surface damage in general, the benefit of time-gated Raman lies in reducing the overall need to push laser parameters to potentially damaging levels when dealing with fluorescent samples, by providing superior background suppression and signal clarity.

In conclusion, while the potential for sample damage exists in any technique using a laser, Timegated® Raman spectroscopy offers a significant advantage. By effectively suppressing the issue of fluorescence, it allows for accurate measurements with moderate laser power, ensuring that you obtain the high-quality spectral data you need without damaging your precious samples.

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