Collisional Excitation of H 2O by H 2 Molecules

Phillips, Timothy R.; Maluendes, Sergio A.; Green, Sheldon

doi:10.1086/192372

Cited by 93 publications

(143 citation statements)

References 0 publications

Supporting

Mentioning

132

Contrasting

Order By: Relevance

“…Another important question is the accuracy of cross-sections with respect to the number of closed channels of the H 2 molecule. Phillips et al (1996); Dubernet & Grosjean (2002) already showed that the j 2 = 2 level has a strong influence on inelastic cross-sections involving no energy transfer in H 2 . Therefore these authors chose basis sets of the type B(n, 2), while Grosjean et al (2003) used a B(n, 3) basis set.…”

Section: Basis Set Convergence: Methodology In Choosing An Appropriatmentioning

confidence: 99%

“…Phillips et al (1996) had already pointed out that this method was not correct for temperatures up to 140 K. Figures 6, 7 show that scaled H 2 O + He rate coefficients underestimate both the j 2 = 0 effective and thermalized rate coefficients, with ratios as large as 1000. The largest ratios occur for transitions dominated by internal energy transfer between H 2 and H 2 O.…”

Section: Underestimation Of Rate Coefficients By Scaled He and Qct Camentioning

confidence: 95%

“…Comparison with the H 2 O + H 2 effective rate coefficients of Phillips et al (1996) Comparison with effective rate coefficients of Phillips et al (1996) can only be performed for the first 10 levels of o-H 2 O and for temperatures in the range 20 K to 140 K. The ratios of effective rate coefficients, given in Table 8, decrease slightly with temperature. This certainly reflects the decreasing influence of the difference between the two different PES (Phillips et al 1994;Faure et al 2005a) as temperature increases.…”

Section: Underestimation Of Rate Coefficients By Scaled He and Qct Camentioning

confidence: 99%

“…Using this PES, Phillips et al (1996) computed rate coefficients for rotational de-excitation among the first 5 ortho and para levels of water with H 2 ( j = 0, 1) for temperatures ranging from 20 K to 140 K. Dubernet & Grosjean (2002) and Grosjean et al (2003) extended this work down to 5 K and pointed out that such low temperature rates are highly sensitive to a proper description of resonances.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature

Dubernet

Daniel

Grosjean

et al. 2009

A&A

102

163

View full text Add to dashboard Cite

Aims. Our objective is to obtain the best possible set of rotational (de)-excitation state-to-state and effective rate coefficients for temperatures up to 1500 K. We present state-to-state rate coefficients among the 45 lowest levels of o-H 2 O with H 2 ( j 2 = 0) and Δ j 2 = 0, +2, as well as with H 2 ( j 2 = 2) and Δ j 2 = 0, −2. In addition and only for the 10 lowest energy levels of o-H 2 O, we provide state-to-state rate coefficients involving j 2 = 4 with Δ j 2 = 0, −2 and j 2 = 2 with Δ j 2 = +2. We give estimates of effective rate coefficients for j 2 = 6, 8. Methods. Calculations are performed with the close coupling (CC) method over the whole energy range, using the same 5D potential energy surface (PES) as the one employed in our latest publication on water. We perform comparisons with coupled states (CS) calculations, with thermalized quasi-classical trajectory (QCT) calculations using the same PES and with previous quantum calculations obtained between T = 20 K and T = 140 K with a different PES. Results. We find that the CS approximation fares extremely badly even at high energy for j 2 different from zero. Comparisons with thermalized QCT calculations show large factors at intermediate temperatures and factors from 1 to 3 at high temperature for the strongest rate coefficients. Finally we stress that scaled collisional rate coefficients obtained with He cannot be used in place of collisional rate coefficients with H 2 .

show abstract

Section: Basis Set Convergence: Methodology In Choosing An Appropriatmentioning

confidence: 99%

Section: Underestimation Of Rate Coefficients By Scaled He and Qct Camentioning

confidence: 95%

Section: Underestimation Of Rate Coefficients By Scaled He and Qct Camentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature

Dubernet

Daniel

Grosjean

et al. 2009

A&A

102

163

View full text Add to dashboard Cite

show abstract

“…We use the collisional rates calculated for H 2 O and He (Green et al 1993), with a scaling factor of 1.4 to correct for the mass difference between H 2 and He. However, a more recent calculation for the collision between H 2 O and ortho-and para-H 2 by Phillips et al (1996) suggests that adopting the collisional rate with He and using the simple scaling factor can give very different rates. Unfortunately, the collisional rates with H 2 were calculated up to 140 K, while the temperature in the circumstellar envelope of an AGB star can be up to 1000 K. If the H 2 O-He rate is underestimated by a large factor, it may have a repercussion on the calculated line fluxes as the water lines are sub-thermally excited in the envelope of W Hya.…”

Section: H 2 O Linesmentioning

confidence: 99%

W Hya through the eye of Odin

Justtanont¹,

Bergman²,

Larsson³

et al. 2005

A&A

View full text Add to dashboard Cite

Abstract. We present Odin observations of the AGB star W Hya in the ground-state transition of ortho-H 2 O, 1 10 − 1 01 , at 557 GHz. The line is clearly of circumstellar origin. Radiative transfer modelling of the water lines observed by Odin and ISO results in a mass-loss rate of (2.5 ± 0.5) × 10 −7 M yr −1 , and a circumstellar H 2 O abundance of (2.0 ± 1.0) × 10 −3 . The inferred mass-loss rate is consistent with that obtained from modelling the circumstellar CO radio line emission, and also with that obtained from the dust emission modelling combined with a dynamical model for the outflow. The very high water abundance, higher than the cosmic oxygen abundance, can be explained by invoking an injection of excess water from evaporating icy bodies in the system. The required extra mass of water is quite small, on the order of ∼0.1 M ⊕ .

show abstract

Gas Phase Chemistry

Schlemmer

Geppert

Wolf

et al. 2014

Laboratory Astrochemistry

View full text Add to dashboard Cite

Collisional Excitation of H 2O by H 2 Molecules

Cited by 93 publications

References 0 publications

Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature

Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature

W Hya through the eye of Odin

Gas Phase Chemistry

Contact Info

Product

Resources

About

Collisional Excitation of H 2O by H 2 Molecules

Cited by 93 publications

References 0 publications

Rotational excitation of ortho-H2O by para-H2 (j2 = 0, 2, 4, 6, 8) at high temperature

Rotational excitation of ortho-H2O by para-H2 (j2 = 0, 2, 4, 6, 8) at high temperature

W Hya through the eye of Odin

Gas Phase Chemistry

Contact Info

Product

Resources

About

Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature

Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature