Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers

• Published in: Review of scientific instruments Vol. 85; no. 8; p. 083109
• Main Authors: Leger, Joel D, Nyby, Clara M, Varner, Clyde, Tang, Jianan, Rubtsova, Natalia I, Yue, Yuankai, Kireev, Victor V, Burtsev, Viacheslav D, Qasim, Layla N, Rubtsov, Grigory I, Rubtsov, Igor V
• Format: Journal Article
• Language: English
• Published: United States 01.08.2014
• ISSN: 1089-7623
• DOI: 10.1063/1.4892480

A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm(-1) to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ~70 as. The anharmonicity of smaller than 10(-4) cm(-1) was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 μrad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy.