A fluorescence monitor method for measuring effective absorption coefficients of molecular rovibronic transitions using tunable dye laser excitation: The case of absorber linewidth narrower than the laser linewidth applied to H2CO

Fairchild, Paul W.; Garland, Nancy; Howard, Willis E.; Lee, Edward K. C.

doi:10.1063/1.440562

Cited by 9 publications

(2 citation statements)

References 7 publications

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“…The first measurements of HCHO absorption cross sections in the UV region were published by McQuigg and Calvert in 1969 . Since then, numerous measurements of HCHO absorption cross sections have been made under a wide range of different experimental parameters including spectral range, resolution, temperature, pressure, and method of HCHO generation. − The resolving powers of many of the earlier techniques employed, however, were not sufficient to observe much of the fine rotational structure present in the HCHO absorption spectrum. More recently, Smith et al measured absorption cross sections across the range 300–340 nm at an estimated resolution of 0.35 cm –1 .…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Absorption Cross Sections of Formaldehyde in the 30285–32890 cm^–1 (304–330 nm) Spectral Region

2012

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Absolute room temperature (294 ± 2 K) absorption cross sections for the Ã(1)A(2)-X̃(1)A(1) electronic transition of formaldehyde have been measured over the spectral range 30,285-32,890 cm(-1) (304-330 nm) using ultraviolet (UV) laser absorption spectroscopy. Accurate high-resolution absorption cross sections are essential for atmospheric monitoring and understanding the photochemistry of this important atmospheric compound. Absorption cross sections were obtained at an instrumental resolution better than 0.09 cm(-1), which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (∼0.07 cm(-1)) and so we were able to resolve all but the most closely spaced lines. Comparisons with previous data as well as with computer simulations have been made. Pressure broadening was studied for the collision partners He, O(2), N(2), and H(2)O and the resulting broadening parameters have been measured and increase with the strength of intermolecular interaction between formaldehyde and the collision partner. The pressure broadening coefficient for H(2)O is an order of magnitude larger than the coefficients for O(2) and N(2) and will contribute significantly to spectral line broadening in the lower atmosphere. Spectral data are made available as Supporting Information.

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Section: Introductionmentioning

confidence: 99%

High-Resolution Absorption Cross Sections of Formaldehyde in the 30285–32890 cm^–1 (304–330 nm) Spectral Region

2012

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“…Numerous measurements of HCHO absorption cross sections have been made under a wide range of different experimental parameters including spectral range, resolution, temperature, pressure, and method of HCHO generation. − As a necessary first step in our laboratory investigations of HCHO photochemistry, we have measured room temperature absolute absorption cross sections obtained at an instrumental resolution better than 0.09 cm –1 measured under conditions of low partial pressure of HCHO (<0.3 Torr) across the same spectral range examined in this study (30 285–32 890 cm –1 ) …”

Section: Introductionmentioning

confidence: 99%

Radical Quantum Yields from Formaldehyde Photolysis in the 30 400–32 890 cm^–1 (304–329 nm) Spectral Region: Detection of Radical Photoproducts Using Pulsed Laser Photolysis–Pulsed Laser Induced Fluorescence

2012

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The relative quantum yield for the production of radical products, H + HCO, from the UV photolysis of formaldehyde (HCHO) has been measured using a pulsed laser photolysis–pulsed laser induced fluorescence (PLP–PLIF) technique across the 30,400–32,890 cm(–1) (304–329 nm) spectral region of the Ã(1)A2–X̃(1)A1 electronic transition. The photolysis laser had a bandwidth of 0.09 cm(–1), which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (0.07 cm(–1)), and the yield spectrum shows detailed rotational structure. The H and HCO photofragments were monitored using LIF of the OH radical as a spectroscopic marker. The OH radicals were produced by rapid reaction of the H and HCO photofragments with NO2. This technique produced an “action” spectrum that at any photolysis wavelength is the product of the H + HCO radical quantum yield and HCHO absorption cross section at the photolysis wavelength and is a relative measurement. Using the HCHO absorption cross section previously obtained in this laboratory, the relative quantum yield was determined two different ways. One produced band specific yields, and the other produced yields averaged over each 100 cm(–1). Yields were normalized to a value of 0.69 at 31,750 cm(–1) based on the current recommendation of Sander et al. (Sander, S. P.; Abbatt, J.; Barker, J. R.; Burkholder, J. B.; Friedl, R. R.; Golden, D. M.; Huie, R. E.; Kolb, C. E.; Kurylo, M. J.; Moortgat, G. K.; et al. Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation No. 17; Jet Propulsion Laboratory: Pasadena, CA, USA, 2011). The resulting radical quantum yields agree well with previous experimental studies and the current JPL recommendation but show greater wavelength dependent structure. A significant decrease in the quantum yield was observed for the 5(0)(1) + 1(0)(1)4(0)(1) combination band centered at 31,125 cm(–1). This band has a low absorption cross section and has little impact on the calculated atmospheric photodissociation rate but is a further indication of the complexity of HCHO photodissociation dynamics.

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Single rotational level fluorescence quantum yields, radiative lifetimes, and nonradiative decay rates of S1 D2CO and H2CO(Ã 1A2, 41): Rotational dependence

Shibuya

Fairchild

Lee

1981

The Journal of Chemical Physics

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A large number of rotational levels in the 41 (v4′ = 1) manifold of S1 formaldehyde were excited in a multipath absorption/fluorescence cell using a pulsed dye laser. Fluorescence decay times (τfD) of D2CO were measured for a number of rotational levels at 10.8 mTorr so that the apparatus could be calibrated for the measurement of fluorescence quantum yields (ΦfH) of many rotational levels of H2CO at varying pressures (1–120 mTorr). For 10.8 mTorr D2CO, the average values of τfD and ΦfD were 4.8±0.3 μsec and 0.66±0.07, respectively. The zero pressure values of ΦfH for H2CO varied randomly from 0.0063 for J′ = 13, K′ = 7 (Erot = 570.9 cm−1) to 0.32 for J′ = 2, K′ = 2 (Erot = 37.1 cm−1), due to a random variation of the nonradiative decay rates. The J′-population averaged value of ΦfH in a given K′ manifold 〈ΦfH(J′)〉K′ shows a trend to decrease with the increase in the K′ quantum number for K′ = 2–6, but becomes nearly constant for K′ = 6–10. The (J′, K′)-population averaged value of ΦfH is 〈ΦfH(J′, K′)〉 = 0.033 and the average value of radiative lifetimes is τrH = 3.3±1.2 μsec for the 41 level.

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A fluorescence monitor method for measuring effective absorption coefficients of molecular rovibronic transitions using tunable dye laser excitation: The case of absorber linewidth narrower than the laser linewidth applied to H2CO

Cited by 9 publications

References 7 publications

High-Resolution Absorption Cross Sections of Formaldehyde in the 30285–32890 cm^–1 (304–330 nm) Spectral Region

High-Resolution Absorption Cross Sections of Formaldehyde in the 30285–32890 cm^–1 (304–330 nm) Spectral Region

Radical Quantum Yields from Formaldehyde Photolysis in the 30 400–32 890 cm^–1 (304–329 nm) Spectral Region: Detection of Radical Photoproducts Using Pulsed Laser Photolysis–Pulsed Laser Induced Fluorescence

Single rotational level fluorescence quantum yields, radiative lifetimes, and nonradiative decay rates of S1 D2CO and H2CO(Ã 1A2, 41): Rotational dependence

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A fluorescence monitor method for measuring effective absorption coefficients of molecular rovibronic transitions using tunable dye laser excitation: The case of absorber linewidth narrower than the laser linewidth applied to H2CO

Cited by 9 publications

References 7 publications

High-Resolution Absorption Cross Sections of Formaldehyde in the 30285–32890 cm–1 (304–330 nm) Spectral Region

High-Resolution Absorption Cross Sections of Formaldehyde in the 30285–32890 cm–1 (304–330 nm) Spectral Region

Radical Quantum Yields from Formaldehyde Photolysis in the 30 400–32 890 cm–1 (304–329 nm) Spectral Region: Detection of Radical Photoproducts Using Pulsed Laser Photolysis–Pulsed Laser Induced Fluorescence

Single rotational level fluorescence quantum yields, radiative lifetimes, and nonradiative decay rates of S1 D2CO and H2CO(Ã 1A2, 41): Rotational dependence

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High-Resolution Absorption Cross Sections of Formaldehyde in the 30285–32890 cm^–1 (304–330 nm) Spectral Region

High-Resolution Absorption Cross Sections of Formaldehyde in the 30285–32890 cm^–1 (304–330 nm) Spectral Region

Radical Quantum Yields from Formaldehyde Photolysis in the 30 400–32 890 cm^–1 (304–329 nm) Spectral Region: Detection of Radical Photoproducts Using Pulsed Laser Photolysis–Pulsed Laser Induced Fluorescence