Measurements and analysis of collisional line-mixing within nuclear hyperfine components of helium broadened HI lines

Recent advances in collisional effects on spectra of molecular gases and their practical consequences

“…From a purely theoretical point of view, Buffa and Tarrini have corrected [218,326] an error in the method elaborated in [324] which rendered it selfinconsistent. However, as stated in [326], this correction does not change the predicted LM effects and "the equations used by Flaud et al [325] yield the same line shape as our equations. "…”

“…This revealed, with good agreement with measured spectra, the overly simplified approximation made in [323] where discrepancies between measurements and calculations were obtained. Similarly, a model based on the IOS approximation and the developments in [324] was proposed [325] and successfully applied to line-broadening and -mixing within nuclear spin hyperfine components of He-broadened lines of HI at room temperature. From a purely theoretical point of view, Buffa and Tarrini have corrected [218,326] an error in the method elaborated in [324] which rendered it selfinconsistent.…”

Pressure broadening and shifting parameters for the spectral lines in the fundamental vibration–rotation bands of HBr and HI in mixtures with rare gases

“…No traces of the hyperfine structure appear in the domain of pressures used in our experiments and the spectral line shapes can be adequately fitted with the Lorentzian profiles. The same applies to the H 127 I lines having a more wide-spread hyperfine structure that collapses already under sub-atmospheric pressures into single features of about 0.04 cm À1 FWHM for the R 1 (0) and P 1 (1) lines [6,10]. Representative line shape fits to the measured P 1 (4) lines of the H 81 Br and H 79 Br isotopomers are depicted in Fig.…”

Line-mixing between rotational Stark components of CH3F self-perturbed and perturbed by helium: Experimental results and IOS analysis

“…An alternative approach to take LM into account is to build the associated relaxation matrix using the Infinite Order Sudden (IOS) approximation [1,8] or its improved Energy Corrected Sudden (ECS) extension [1,9,10]. IOS/ECS models have enabled precise modeling of LM effects for many systems and types of spectra [1], including hyperfine components due to nuclear spin [11,12] and symmetric-top spectra [13,14]. However, quite surprisingly, as shown in Ref.…”