TY - JOUR
T1 - Facile background discrimination in femtosecond stimulated raman spectroscopy using a dual-frequency raman pump technique
AU - Bera, Kajari
AU - Kwang, Siu Yi
AU - Cassabaum, Alyssa A.
AU - Rich, Christopher C.
AU - Frontiera, Renee R.
N1 - Publisher Copyright:
Copyright © 2019 American Chemical Society.
PY - 2019/9/19
Y1 - 2019/9/19
N2 - Femtosecond stimulated Raman spectroscopy (FSRS) is a useful technique for uncovering chemical reaction dynamics by acquiring high-resolution Raman spectra with ultrafast time resolution. However, in FSRS, it can be challenging to discern Raman features from signals arising from transient absorption and other four-wave mixing pathways. To overcome this difficulty, we combine the principles of shifted excitation Raman difference spectroscopy with a simple fixed frequency comb to perform dual-frequency Raman pump FSRS. Through the addition of only two mirrors and a slit to the standard FSRS setup, this method provides Raman spectra at two different excitation wavelengths that can be processed by an automated algorithm to reconstruct the Raman spectrum. Here, we demonstrate the utility of dual-frequency Raman pump FSRS to easily identify Raman signatures by visual inspection for excited-state and ground-state spectra, both on- and off-resonance. We show that previously assigned short-lived vibrations of photoexcited β-carotene are actually not vibrational in nature. We also use crystalline betaine-30 as a challenging test case for this method, as the FSRS spectra contain a number of narrow transient vibronic and non-SRS features. By reliably reducing interference from background signals, the interpretation is substantially more quantitative and enables the future study of new systems, particularly those with small Raman cross-sections or solid-state samples with narrow vibronic features.
AB - Femtosecond stimulated Raman spectroscopy (FSRS) is a useful technique for uncovering chemical reaction dynamics by acquiring high-resolution Raman spectra with ultrafast time resolution. However, in FSRS, it can be challenging to discern Raman features from signals arising from transient absorption and other four-wave mixing pathways. To overcome this difficulty, we combine the principles of shifted excitation Raman difference spectroscopy with a simple fixed frequency comb to perform dual-frequency Raman pump FSRS. Through the addition of only two mirrors and a slit to the standard FSRS setup, this method provides Raman spectra at two different excitation wavelengths that can be processed by an automated algorithm to reconstruct the Raman spectrum. Here, we demonstrate the utility of dual-frequency Raman pump FSRS to easily identify Raman signatures by visual inspection for excited-state and ground-state spectra, both on- and off-resonance. We show that previously assigned short-lived vibrations of photoexcited β-carotene are actually not vibrational in nature. We also use crystalline betaine-30 as a challenging test case for this method, as the FSRS spectra contain a number of narrow transient vibronic and non-SRS features. By reliably reducing interference from background signals, the interpretation is substantially more quantitative and enables the future study of new systems, particularly those with small Raman cross-sections or solid-state samples with narrow vibronic features.
UR - http://www.scopus.com/inward/record.url?scp=85072509819&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85072509819&partnerID=8YFLogxK
U2 - 10.1021/acs.jpca.9b02473
DO - 10.1021/acs.jpca.9b02473
M3 - Article
C2 - 31486646
AN - SCOPUS:85072509819
SN - 1089-5639
VL - 123
SP - 7932
EP - 7939
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 37
ER -