TY - JOUR
T1 - Sub-Doppler spectra of infrared hyperfine transitions of nitric oxide using a pulse modulated quantum cascade laser
T2 - rapid passage, free induction decay, and the ac Stark effect
AU - Duxbury, Geoffrey
AU - Kelly, James F.
AU - Blake, Thomas A.
AU - Langford, Nigel
PY - 2012/5/7
Y1 - 2012/5/7
N2 - Using a low power, rapid (nsec) pulse-modulated quantum cascade (QC) laser, collective coherent effects in the 5 mu m spectrum of nitric oxide have been demonstrated by the observation of sub-Doppler hyperfine splitting and also Autler-Townes splitting of Doppler broadened lines. For nitrous oxide, experiments and model calculations have demonstrated that two main effects occur with pulse-modulated (chirped) quantum cascade lasers: free induction decay signals, and signals induced by rapid passage during the laser chirp. In the open shell molecule, NO, in which both Lambda-doubling splitting and hyperfine structure occur, laser field-induced coupling between the hyperfine levels of the two Lambda-doublet components can induce a large ac Stark effect. This may be observed as sub-Doppler structure, field-induced splittings, or Autler-Townes splitting of a Doppler broadened line. These represent an extension of the types of behaviour observed in the closed shell molecule nitrous oxide, using the same apparatus, when probed with an 8 mu m QC laser. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4710542]
AB - Using a low power, rapid (nsec) pulse-modulated quantum cascade (QC) laser, collective coherent effects in the 5 mu m spectrum of nitric oxide have been demonstrated by the observation of sub-Doppler hyperfine splitting and also Autler-Townes splitting of Doppler broadened lines. For nitrous oxide, experiments and model calculations have demonstrated that two main effects occur with pulse-modulated (chirped) quantum cascade lasers: free induction decay signals, and signals induced by rapid passage during the laser chirp. In the open shell molecule, NO, in which both Lambda-doubling splitting and hyperfine structure occur, laser field-induced coupling between the hyperfine levels of the two Lambda-doublet components can induce a large ac Stark effect. This may be observed as sub-Doppler structure, field-induced splittings, or Autler-Townes splitting of a Doppler broadened line. These represent an extension of the types of behaviour observed in the closed shell molecule nitrous oxide, using the same apparatus, when probed with an 8 mu m QC laser. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4710542]
KW - high-speed optical techniques
KW - hyperfine structure
KW - infrared spectra
KW - nitrogen compounds
KW - Stark effect
UR - http://www.scopus.com/inward/record.url?scp=84862894537&partnerID=8YFLogxK
U2 - 10.1063/1.4710542
DO - 10.1063/1.4710542
M3 - Article
SN - 0021-9606
VL - 136
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 17
M1 - 174319
ER -