Transcript HONO Columbus 2010.pptx

Vincent Sironneau, J.-M. Flaud,
J.Orphal1, I. Kleiner, P. Chelin
Laboratoire Interuniversitaire des Systèmes
Atmosphériques (LISA), Créteil
1Institute for Meteorology and Climate Research
(IMK), Karlsruhe
Columbus 2010
Nitrous acid HONO
 Observed for the first time by Perner and Platt in 1979
 Rapid photolysis (lifetime ~ 13 minutes)
HONO  hn   390nm)  OH  NO
 Hydroxyl radical plays a significant role in the tropospheric
ozone formation
 Atmospheric detection
 In the UV region by DOAS method (Differential Optical Absorption
Spectroscopy)
 In the IR region around 1263cm-1 (n3 band) with a tunable diode laser
in 2001
 Abundance of:

Peak night-time 8 to 14 ppbv
D. Perner and U. Platt, Geophys. Res. Lett. 6, 917–920 (1979)
C.L. Schiller, S. Locquiao, and T.J. Jonhson et al, J. Atmos. Chem. 40, 275–293 (2001)
Ab-initio calculations
 Interest for molecular dynamics and
ab-initio calculation
 One of the smallest molecule having two
isomers
 cis-trans, trans-cis isomerization
cis-HONO
 Structure calculations, potential
energy surfaces
Thanks to information given by
high resolution spectroscopy on all the
isotopes
 Benchmarks:
 trans-cis energy difference
trans-HONO
 trans-cis barrier height
D. Luckhaus, Chem. Phys. 304 (2004) 79-90.
F. Richter, M. Hochlaf, P. Rosmus, F. Gatti, H.-D. Meyer, J. Chem. Phys. 120 (2004) 1306-1317.
Energy difference between the vibrational ground
states of trans-HONO and cis-HONO
Rotationalspectra,
spectra,
Rotational
calculatedand
and
calculated
observed,ofofDONO
observed,
HONO
with the
with
the different
different
contributions
contributions
N. of lines
rms in cm-1
trans-HONO
1466
0,00046
Energy
difference (experiments)
DE=141 to
-1
cis-HONO
791
0,00042
225cm
trans-DONO
357DE=97 to0,00043
By ab-initio
calculations
385cm-1
cis-DONO
230
0,00034
A. Dehayem-Kamadjeu, O. Pirali, J. Orphal, I. Kleiner, P.-M. Flaud, J. Mol. Spectrosc. 234 (2005) 182-189
Method

Fitting of observed lines
and calculation of their
surfaces
Relative intensities of the
transitions

Determination of :


the « relative » permanent
dipoles moment (b
component)
their rotational correction in
function of rotational
quantum numbers for the
trans and cis-HONO and
trans and cis-DONO
Example of fitting lines with Kelly-Fit code
These values were scaled
to the absolute values
derived from Stark effect
measurements
Absolute intensities
J. Orphal, J.-M. Flaud, Q. Kou, F. Kwabia Tchana, O. Pirali, J. Mol. Struct. 742 (2005) 153-159
Concentration of the two isomers in the
absorption cell
J range
K range
a
cis
I exp
(cm 1 )
N cis

l
cis
I abs (cm / molecule )
V
I
trans
exp
1
(cm )
N trans

l
trans
I abs (cm / molecule )
V



No. of lines
trans-HONO
9-43
5-19
120
cis-HONO
9-41
6-22
94
trans-DONO
13-45
5-20
46
cis-DONO
14-39
8-20
31
Number of lines included in the intensity
fits and range covered in J and Ka
Values calculated for each lines and then averaged
But unfortunately the transition with low J and Ka are
not observed in the spectral range covered here
Concentration ratio between the two isomers
 N cis 

DE  kT ln 
 N trans 
Results and discussion
HONO
DONO
ΔE cis-trans
99±25
136±30
ΔEDONO(cor)
-
114 ± 32
ΔEHONO(av)
107±26
-
 Energy differences between the ground
states of cis and trans isomers with and
without ZPE correction
 Values in cm-1
 Lower
than the
previous
values
C.m
Debye
C.m
Debye
Operator
trans-HONO
cis-HONO
4.493×10 agreement
1.347
4.650×10
1.394
 In good
with the latest
fx
{ify,Jz}
{fz,iJy}
-30
-1.10(20)×10-32
a
-3.309(60)×10-3
ab-initio
value
-
-30
-1.85(32)×10-32
-5.56(95)×10-3
5.57(150)×10-33
1.67(45)×10-3
Number of
lines
120
a
94
 Due to the correction
of-1 the
ΔEHONO in cm
dipole
Authormoment:
Experiment ab-initio
Badger [22]than
177±90
cis stronger
for the trans
McGraw [1]
186±350
Ncis141±35
increases
Bongartz [21]Ntrans
225±20
Varma [20]
ratio
Luckhaus [10]
∆E decreases
Richter
[12]
367
97
This work correction
107±26 the value
 Without
is ∆E=128±25cm-1
V. Sironneau, J.-M. Flaud, J. Orphal, I. Kleiner, P. Chelin, J. Mol. Spectrosc. 259 (2010) 100-104
Conclusions
 Measurements of the FIR lines intensities for the both




isomers of HONO and DONO
Determination of the rotational corrections of the btype permanent dipole moments for HONO and
DONO
Line list available for HONO (position and intensity)
Redetermination of the energy difference between the
trans and cis-species of HONO (107cm-1)
Value in good agreement with the most recent abinitio calculation (97cm-1)
Thanks for your attention