Dpto. Química Física, Fac. Ciencia y Tecnología, Universidad del País Vasco-UPV/EHU, B° Sarriena, s/n, 48940 Leioa, Spain.
J Phys Chem A. 2012 Jun 28;116(25):6798-803. doi: 10.1021/jp303937h. Epub 2012 Jun 8.
Mass-resolved excitation spectroscopic techniques are usually limited to systems with a chromophore, that is, a functional group with electronic transitions in the Vis/UV, with lifetimes from hundreds of picoseconds to some microseconds. In this paper, we expand such techniques to any system, by using a combination of nanosecond IR pulses with nonresonant ionization with 800 nm femtosecond laser pulses. Furthermore, we demonstrate that the technique can achieve conformational specificity introducing an additional nanosecond IR laser. As a proof-of-principle, we apply the technique to the study of phenol(H(2)O)(1), propofol(H(2)O)(1) γ-butyrolactone(H(2)O)(n), n = 1-3, and (H(2)O)(2) complexes. While monohydrated phenol and propofol clusters permit a direct comparison with a well-studied system including an aromatic chromophore, γ-butyrolactone is a cyclic nonaromatic molecule, whose mass-resolved spectroscopy cannot be tackled by conventional techniques. Finally, we further demonstrate the potential of the technique by obtaining the first mass-resolved IR spectrum of the neutral water dimer, a nice example of a system whose ionization-based detection had not been possible to date.
质量分辨激发光谱技术通常仅限于具有发色团的系统，即具有在可见/紫外范围内的电子跃迁的官能团，其寿命从数百皮秒到数微秒不等。在本文中，我们通过使用纳秒 IR 脉冲与 800nm 飞秒激光脉冲的非共振电离相结合，将该技术扩展到任何系统。此外，我们证明该技术可以通过引入额外的纳秒 IR 激光来实现构象特异性。作为原理验证，我们将该技术应用于苯酚 (H(2)O)(1)、丙泊酚 (H(2)O)(1)γ-丁内酯 (H(2)O)(n)，n=1-3 和 (H(2)O)(2) 配合物的研究。虽然一水合苯酚和丙泊酚团簇允许与包括芳香发色团的研究良好的系统进行直接比较，但γ-丁内酯是一种环状非芳香分子，其质量分辨光谱不能用传统技术解决。最后，我们通过获得中性水二聚体的第一个质量分辨红外光谱进一步证明了该技术的潜力，这是一个很好的例子，说明目前还不可能基于电离检测到该系统。
