van Outersterp Rianne E, Martens Jonathan, Peremans André, Lamard Laurent, Cuyckens Filip, Oomens Jos, Berden Giel
Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
Laboratoire Physique de la Matière et du Rayonnement (P.M.R), Université de Namur, 5000 Namur, Belgium.
Analyst. 2021 Nov 22;146(23):7218-7229. doi: 10.1039/d1an01406d.
Infrared ion spectroscopy is increasingly recognized as a method to identify mass spectrometry-detected analytes in many (bio)chemical areas and its integration in analytical laboratories is now on the horizon. Commercially available quadrupole ion trap mass spectrometers are attractive ion spectroscopy platforms but operate at relatively high pressures. This promotes collisional deactivation which directly interferes with the multiple-photon excitation process required for ion spectroscopy. To overcome this, infrared lasers having a high instantaneous power are required and therefore a majority of analytical studies have been performed at infrared free electron laser facilities. Proliferation of the technique to routine use in analytical laboratories requires table-top infrared lasers and optical parametric oscillators (OPOs) are the most suitable candidates, offering both relatively high intensities and reasonable spectral tuning ranges. Here, we explore the potential of a range of commercially available high-power OPOs for ion spectroscopy, comparing systems with repetition rates of 10 Hz, 20 kHz, 80 MHz and a continuous-wave (cw) system. We compare the performance for various molecular ions and show that the kHz and MHz repetition-rate systems outperform cw and 10 Hz systems in photodissociation efficiency and offer several advantages in terms of cost-effectiveness and practical implementation in an analytical laboratory not specialized in laser spectroscopy.
红外离子光谱法在许多（生物）化学领域作为一种识别质谱检测到的分析物的方法正日益受到认可，并且它在分析实验室中的整合如今已指日可待。市售的四极杆离子阱质谱仪是颇具吸引力的离子光谱平台，但在相对较高的压力下运行。这会促进碰撞失活，直接干扰离子光谱所需的多光子激发过程。为克服这一问题，需要具有高瞬时功率的红外激光器，因此大多数分析研究是在红外自由电子激光设施上进行的。该技术在分析实验室中的常规应用需要台式红外激光器，而光学参量振荡器（OPO）是最合适的候选者，它既具有相对较高的强度，又有合理的光谱调谐范围。在此，我们探索一系列市售高功率OPO用于离子光谱的潜力，比较重复频率为10 Hz、20 kHz、80 MHz的系统以及一个连续波（cw）系统。我们比较了各种分子离子的性能，结果表明kHz和MHz重复频率系统在光解离效率方面优于cw和10 Hz系统，并且在成本效益以及在非专门从事激光光谱研究的分析实验室中的实际应用方面具有若干优势。
