Detection of the H2PS free radical by laser spectroscopy

Robert Grimminger*, Dennis J. Clouthier*, and Riccardo Tarroni†

*Department of Chemistry, University of Kentucky, Lexington KY†Dipartimento di Chimica Fisica ed Inorganica, Università di Bologna, 40136 Bologna, Italy

Why study H2PS?

Phosphorus?

Spin labels

Production of jet-cooled radicals

5% H2 in Ar

H2PS

Cl3PS (liq.)

3% H2 in Ar +3% D2 in Ar5% D2 in Ar

D2PSH2PSD2PSHDPS

Molecular orbitals of H2PS

A2 X~

π (12a′)

n (4a″)

π* (13a′)

A2 A~

A2 B~

Energy (cm-1) 0 4,600 20,800

Calculations done by Riccardo Tarroni using CCSD and CCSD-EOM using aug-cc-pV(T+d)Z basis

Calculated geometry for lowest electronic states

State r (PS) Å r (PH)Å (HPS)° (HPH)° (oop)°

X� 2A 1.979 1.402 109.0 99.8 59.7

A 2A 2.139 1.413 94.2 90.4 84.1

B� 2A 2.114 1.411 109.9 94.4 59.9

a

c

b

H

H

P Sθ

CCSD and CCSD-EOM using aug-cc-pV(T+d)Z basis

Low resolution LIF spectra

000

000

103

104

102

203

10

1043

10

1032 3

03

204 1

02043

10

1032

303

10

1043

2031

03

102

ν2 = PH sym. Bendν3 = PS stretchν4 = HPH wag

104

Calc. = CCSD and CCSD-EOM using aug-cc-pV(T+d)Z basis

Obs. isotope shift = 2.9 cm-1

Calc. isotope shift = 3.0 cm-1

ConstantH2PS D2PS

obs. calc. obs. calc.ω1

0 (a´) ··· 2394 ··· 1719ω2

0 (a´) 1062.1(6) 1137 770.0(3) 817ω3

0 (a´) 470.3(5) 525 451.4(2) 492ω4

0 (a´) 823.9(10) 843 643.0(5) 661ω5

0 (a˝) ··· 2402 ··· 1730ω6

0 (a˝) ··· 670 ··· 486x33 ··· -6.3(1)x34 -7.8(4) -4.5(1)

x44 -2.9(1) -2.55(3)

Total LIF of a mixture of isotopologs

H2PS

D2PS

HDPS

Pump LaserTunable Dye laser

Synchronous-scan LIF technique

PMT

15000160001700018000190002000021000220002300024000Laser:

Offset: 450

cm-1

cm-1

HDPS sync-scan LIF

1-6

-13

cm 532.4 rock HPD )(

cm 452.4stretch S-P )(

a

a

Analysis of emission spectra103

000

403

14

14

14

13

13

13

12

12

Calc. =CCSD and CCSD-EOM using aug-cc-pV(T+d)Z basis

ν2 = PH sym. Bendν3 = PS stretchν4 = HPH wag

Constant(cm-1)

H2PS D2PS HDPS

obs. calc. obs. calc. obs. calc.

ω10 (a´) ··· 2446 ··· 1751 ··· 2455

ω20 (a´) 1088.7(14) 1142 812.2(9) 824 976.7(4) 1007

ω30 (a´) 681.1(4) 694 613.3(3) 614 594.8(2) 600

ω40 (a´) 481.1(4) 422 389.0(4) 349 429.1(4) 382

ω50 (a˝) ··· 2465 ··· 1776 ··· 1763

ω60 (a˝) ··· 782 ··· 568 698(1) 721

High-resolution of the H2PS 00 band0

Geometry of H2PS

Calculated out-of-plane angle

Molecule X� B�

H2PO 48° 67°

H2AsO 59° 70°

H2PS 60° 60°

Cl2PS 47° 63°

F2PS 49° 67°

H

H

P Sθ

Out-of-plane angle

CCSD and CCSD-EOM using aug-cc-pV(T+d)Z basis

Constant(cm-1)

X� B�

A [4.85402] 4.727(5)[4.93042]

B 0.2517(4)[0.249317]

0.2137(5)[0.219462]

B-C [0.4502×10-2] [0.2570×10-2]

εaa [-0.42758] 0.155(4)

T0 20004.337(4)

–

Walsh diagram for H2PS system

Orbital energies at B3LYP/aug-cc-pV(T+d)Z for H2PS anion

Conclusions

• First spectroscopic observation of H2PS

• H2PS has been characterized by LIF and SVL emission spectroscopy

• Our analysis identifies the observed transition as B� 2A´– X� 2A´, as predicted by our ab initio calculations