Applied Physics B

, Volume 75, Issue 6–7, pp 755–761

Off-axis continuous-wave cavity-enhanced absorption spectroscopy of narrow-band and broadband absorbers using red diode lasers

  • V.L. Kasyutich
  • C.E. Canosa-Mas
  • C. Pfrang
  • S. Vaughan
  • R.P. Wayne

DOI: 10.1007/s00340-002-1032-3

Cite this article as:
Kasyutich, V., Canosa-Mas, C., Pfrang, C. et al. Appl Phys B (2002) 75: 755. doi:10.1007/s00340-002-1032-3

Abstract.

We present an application of continuous-wave (cw) cavity-enhanced absorption spectroscopy (CEAS) with off-axis alignment geometry of the cavity and with time integration of the cavity output intensity for detection of narrow-band and broadband absorbers using single-mode red diode lasers at λ=687.1 nm and λ=662 nm, respectively. Off-axis cw CEAS was applied to kinetic studies of the nitrate radical using a broadband absorption line at λ=662 nm. A rate constant for the reaction between the nitrate radical and E-but-2-eneof (3.78±0.17)×10-13 cm3 molecule-1 s-1 was measured using a discharge-flow system. A nitrate-radical noise-equivalent (1σ≡ root-mean-square variation of the signal) detection sensitivity of 5.5×109 molecule cm-3 was achieved in a flow tube with a diameter of 4 cm and for a mirror reflectivity of ∼99.9% and a lock-in amplifier time constant of 3 s. In this case, a noise-equivalent fractional absorption per one optical pass of 1.6×10-6 was demonstrated at a detection bandwidth of 1 Hz. A wavelength-modulation technique (modulation frequency of 10 kHz) in conjunction with off-axis cw CEAS has also been used for recording 1f- and 2f-harmonic spectra of the RR(15) absorption of the b1Σg+-X3Σg- (1,0) band of molecular oxygen at \(\overline{\nu}\)=14553.947 cm-1. Noise-equivalent fractional absorptions per one optical pass of 1.35×10-5, 6.9×10-7 and 1.9×10-6 were obtained for direct detection of the time-integrated cavity output intensity, 1f- and 2f-harmonic detection, respectively, with a mirror reflectivity of ∼99.8%, a cavity length of 0.22 m and a detection bandwidth of 1 Hz.

PACS: 42.55.Px; 42.62.Fi; 42.68.Ca; 82.30.Cf 

Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • V.L. Kasyutich
    • 1
  • C.E. Canosa-Mas
    • 1
  • C. Pfrang
    • 1
  • S. Vaughan
    • 1
  • R.P. Wayne
    • 1
  1. 1.Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UKGB

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