Photochemical data discussion of Format and Error Estimates




НазваниеPhotochemical data discussion of Format and Error Estimates
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HF + h H + F



The ultraviolet absorption spectrum of HF has been studied by Safary et al. [266]. The onset of absorption occurs at  < 170 nm, so that photodissociation of HF should be unimportant in the stratosphere.


HCl + h H + Cl



The absorption cross sections of HCl, listed in Table 34, are taken from the work of Inn [134].

Table 34. Absorption Cross Sections of HCl Vapor






(nm)


1020

(cm2)



(nm)

1020

(cm2)

140 211 185 31.3

145 281 190 14.5

150 345 195 6.18

155 382 200 2.56

160 332 205 0.983

165 248 210 0.395

170 163 215 0.137

175 109 220 0.048

180 58.8















HOCl + h OH + Cl



The absorption cross sections of HOCl vapor have been measured by several groups. Molina and Molina [201] and Knauth et al. [150] produced this species using equilibrium mixtures with Cl2O and H2O; their results provided the basis for the earlier recommendation. More recently, Mishalanie et al. [197] and Permien et al. [243] used a dynamic source to generate the HOCl vapor. The cross section values reported by Molina and Molina [201], Mishalanie et al. [197], and Permien et al. [243] are in reasonable agreement between 250 and 330 nm. In this wavelength range, the values reported by Knauth et al. [150] are significantly smaller, e.g., a factor of 4 at 280 nm. Beyond 340 nm, the cross sections of Mishalanie et al. are much smaller than those obtained by the other three groups: at 365 nm, the discrepancy is about an order of magnitude.


The recent results by Burkholder [33] are in excellent agreement with the work of Knauth et al. [150], but in poor agreement with the more recent measurements of Mishalanie et al. [197] and Permien et al. [243]. The discrepancies can be attributed mostly to difficulties in correcting the measured absorptions for the presence of Cl2 and Cl2O. The recommended values, taken from the work of Burkholder [33], are listed in Table 35. In this work, several control experiments were carried out in order to check the internal consistency of the data. More recent work by Jungkamp et al. [149] yields cross section values in excellent agreement with this recommendation.


Molina et al. [212] observed production of OH radicals in the laser photolysis of HOCl around 310 nm, and Butler and Phillips [45] found no evidence for O-atom production at 308 nm, placing an upper limit of ~0.02 for the primary quantum yield for the HCl + O channel. Vogt and Schindler [318] used broadband photolysis in the 290 - 390 nm wavelength range, determining a quantum yield for OH production of >0.95.

Table 35. Absorption Cross Sections of HOCl






(nm)


1020

(cm2)



(nm)

1020

(cm2)



(nm)

1020

(cm2)




200

7.1

262

9.3

322

4.6

202

6.1

264

8.3

324

4.3

204

5.6

266

7.4

326

4.2

206

5.4

268

6.6

328

3.8

208

5.5

270

6.0

330

3.5

210

5.7

272

5.5

332

3.3

212

6.1

274

5.2

334

3.1

214

6.6

276

4.9

336

2.7

216

7.5

278

4.8

338

2.5

218

8.4

280

4.7

340

2.4

220

9.7

282

4.8

342

2.1

222

10.9

284

4.8

344

1.8

224

12.2

286

4.9

346

1.8

226

13.5

288

5.1

348

1.7

228

15.0

290

5.3

350

1.5

230

16.4

292

5.4

352

1.3

232

17.7

294

5.6

354

1.3

234

18.7

296

5.8

356

1.2

236

19.7

298

5.9

358

1.0

238

20.3

300

6.0

360

0.8

240

20.7

302

6.0

362

1.0

242

21.0

304

6.1

364

1.0

244

20.5

306

6.0

366

0.9

246

19.6

308

6.0

368

0.8

248

18.6

310

5.9

370

0.8

250

17.3

312

5.7

372

1.0

252

15.9

314

5.6

374

0.8

254

14.6

316

5.4

376

0.8

256

13.2

318

5.1

378

0.6

258

11.8

320

4.9

380

0.8

260

10.5



























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