连续波长可调,连续波激光器理想的紫外拉曼光谱

IF 2.4 3区 化学 Q2 SPECTROSCOPY
Ryan D. Roppel, Sanford A. Asher
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引用次数: 0

摘要

我们利用一种新型的、高功率的、可调谐的连续波(CW)深紫外激光器来测量具有高信噪比(SNR)的酚酸盐溶液的共振拉曼光谱。在紫外共振拉曼(UVRR)中,激发光与发色团的耦合增加可以将分子转移到激发态,从而引起加热和光化学反应的增加。深紫外激光器传统上利用高峰值功率实现从可见光到近红外光的有效单次非线性转换。非线性现象,如瞬态自由基的形成、拉曼饱和、热加热和介电击穿,会引入外来光源,使拉曼光谱的解释复杂化。介电击穿会增加基线,增加噪声,有时会使探测器饱和,从而阻止拉曼探测。自发拉曼散射强度应与激发光强度成线性比例。然而,在脉冲激光激励下,这种线性行为并不总是发生。这是因为受激拉曼散射可以引起超线性强度响应,或者瞬态吸收可以引起亚线性强度响应。连续波激光激发的电场比典型脉冲激光激发的电场小得多。这消除了非线性响应。我们的新型连续波激光器的几何结构使谐波产生腔具有高增益,从而实现高谐波产生效率。对于短至206nm的波长,深紫外的平均功率为30mw。在这里的工作中,我们证明了连续波激励通常是共振拉曼测量的理想选择,可以降低光谱复杂性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Continuously wavelength tunable, continuous wave laser ideal for UV Raman spectroscopy

Continuously wavelength tunable, continuous wave laser ideal for UV Raman spectroscopy

Continuously wavelength tunable, continuous wave laser ideal for UV Raman spectroscopy

We utilize a novel, high-power, tunable, continuous wave (CW) deep UV laser to measure resonance Raman spectra of phenolate solutions with high signal-to-noise ratios (SNR). In UV resonance Raman (UVRR), increased coupling of the excitation light with a chromophore can transfer molecules into excited states that cause increased heating and photochemistry. Deep UV lasers have traditionally utilized high peak powers to enable efficient single-pass nonlinear conversion from visible into near infrared light. Nonlinear phenomena such as the formation of transient radical species, Raman saturation, thermal heating, and dielectric breakdown can introduce extraneous light sources that can complicate the interpretation of the Raman spectrum. Dielectric breakdown can increase the baseline, increase noise, and sometimes saturate the detector, preventing Raman detection. Spontaneous Raman scattering intensities should scale linearly with the excitation light intensity. However, this linear behavior does not always occur with pulsed laser excitation. This occurs because stimulated Raman scattering can cause a superlinear intensity response, or transient absorption can cause sublinear intensity responses. CW laser excitation excites samples with electric fields that are much lower than typical pulsed laser excitation. This eliminates the nonlinear responses. The geometry of our new CW laser enables high gain in the harmonic generation cavities that achieve high harmonic generation efficiencies. Average power in the deep UV is >30 mW for wavelengths as short as 206 nm. In the work here, we demonstrate that CW excitation is ideal for resonance Raman measurements in general to reduce spectral complexity.

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来源期刊
CiteScore
5.40
自引率
8.00%
发文量
185
审稿时长
3.0 months
期刊介绍: The Journal of Raman Spectroscopy is an international journal dedicated to the publication of original research at the cutting edge of all areas of science and technology related to Raman spectroscopy. The journal seeks to be the central forum for documenting the evolution of the broadly-defined field of Raman spectroscopy that includes an increasing number of rapidly developing techniques and an ever-widening array of interdisciplinary applications. Such topics include time-resolved, coherent and non-linear Raman spectroscopies, nanostructure-based surface-enhanced and tip-enhanced Raman spectroscopies of molecules, resonance Raman to investigate the structure-function relationships and dynamics of biological molecules, linear and nonlinear Raman imaging and microscopy, biomedical applications of Raman, theoretical formalism and advances in quantum computational methodology of all forms of Raman scattering, Raman spectroscopy in archaeology and art, advances in remote Raman sensing and industrial applications, and Raman optical activity of all classes of chiral molecules.
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