# The singlet-triplet absorption and photodissociation of the HOCl, HOBr, and HOI molecules calculated by the MCSCF quadratic response method

## Abstract

The molecular absorption spectra of hypochlorous, hypobromous, and hypoiodous acids have been studied by multiconfiguration self-consistent field (MCSCF) calculations with linear and quadratic response techniques. The complete form of the spin-orbit coupling (SOC) operator is accounted. The singlet-triplet transition to the lowest triplet state {sup 3}A{double{underscore}prime} {l{underscore}arrow} X{sup 1}A{prime} is shown to be responsible for the weak long-wavelength tail absorption and photodissociation in these molecules. The transition is polarized along the O-X bond (X = Cl, Br, I) and has an oscillator strength equal 6 x 10{sup {minus}6}, 8 x 10{sup {minus}5}, and 2 x 10{sup {minus}4} for hypochlorous, hypobromous, and hypoiodous acids, respectively. The second singlet-triplet transition {sup 3}A{prime} {l{underscore}arrow} X{sup 1}A{prime} comes to the region of the first singlet-singlet {sup 1}A{double{underscore}prime} {l{underscore}arrow} X{sup 1}A{prime} absorption and contributes significantly to the total cross-section at wavelengths {lambda} {approx} 300--320 nm (X = Cl), {lambda} {approx} 340--360 nm (X = Br), and {lambda} {approx} 400 nm (X = I). In the last case the singlet-triplet transition {sup 3}A{prime} {l{underscore}arrow} X{sup 1}A{prime} produces predominant contribution to HOI absorption in the visible region. All states are dissociative, so the singlet-triplet absorption contributes to the yield of photolysis in the important near-UV and visiblemore »

- Authors:

- Publication Date:

- Research Org.:
- Linkoeping Univ. (SE)

- OSTI Identifier:
- 20000055

- Resource Type:
- Journal Article

- Journal Name:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

- Additional Journal Information:
- Journal Volume: 103; Journal Issue: 36; Other Information: PBD: 9 Sep 1999; Journal ID: ISSN 1089-5639

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 54 ENVIRONMENTAL SCIENCES; HYPOCHLOROUS ACID; HYPOIODOUS ACID; MATHEMATICAL MODELS; L-S COUPLING; TRIPLETS; ENERGY LEVELS; PHOTOLYSIS; ATMOSPHERIC CHEMISTRY

### Citation Formats

```
Minaev, B.F.
```*The singlet-triplet absorption and photodissociation of the HOCl, HOBr, and HOI molecules calculated by the MCSCF quadratic response method*. United States: N. p., 1999.
Web. doi:10.1021/jp990203d.

```
Minaev, B.F.
```*The singlet-triplet absorption and photodissociation of the HOCl, HOBr, and HOI molecules calculated by the MCSCF quadratic response method*. United States. doi:10.1021/jp990203d.

```
Minaev, B.F. Thu .
"The singlet-triplet absorption and photodissociation of the HOCl, HOBr, and HOI molecules calculated by the MCSCF quadratic response method". United States. doi:10.1021/jp990203d.
```

```
@article{osti_20000055,
```

title = {The singlet-triplet absorption and photodissociation of the HOCl, HOBr, and HOI molecules calculated by the MCSCF quadratic response method},

author = {Minaev, B.F.},

abstractNote = {The molecular absorption spectra of hypochlorous, hypobromous, and hypoiodous acids have been studied by multiconfiguration self-consistent field (MCSCF) calculations with linear and quadratic response techniques. The complete form of the spin-orbit coupling (SOC) operator is accounted. The singlet-triplet transition to the lowest triplet state {sup 3}A{double{underscore}prime} {l{underscore}arrow} X{sup 1}A{prime} is shown to be responsible for the weak long-wavelength tail absorption and photodissociation in these molecules. The transition is polarized along the O-X bond (X = Cl, Br, I) and has an oscillator strength equal 6 x 10{sup {minus}6}, 8 x 10{sup {minus}5}, and 2 x 10{sup {minus}4} for hypochlorous, hypobromous, and hypoiodous acids, respectively. The second singlet-triplet transition {sup 3}A{prime} {l{underscore}arrow} X{sup 1}A{prime} comes to the region of the first singlet-singlet {sup 1}A{double{underscore}prime} {l{underscore}arrow} X{sup 1}A{prime} absorption and contributes significantly to the total cross-section at wavelengths {lambda} {approx} 300--320 nm (X = Cl), {lambda} {approx} 340--360 nm (X = Br), and {lambda} {approx} 400 nm (X = I). In the last case the singlet-triplet transition {sup 3}A{prime} {l{underscore}arrow} X{sup 1}A{prime} produces predominant contribution to HOI absorption in the visible region. All states are dissociative, so the singlet-triplet absorption contributes to the yield of photolysis in the important near-UV and visible region close to the intense solar actinic flux. Contributions to the removal mechanisms for atmospheric HOCl, HOBr, and HOI species are shortly discussed. The minor loss process of ozone in troposphere because of the HOI reservoir sink is getting evident on the ground of this calculations. The importance of SOC accounting for atmospheric photochemistry problems is stressed.},

doi = {10.1021/jp990203d},

journal = {Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory},

issn = {1089-5639},

number = 36,

volume = 103,

place = {United States},

year = {1999},

month = {9}

}